Helena AP ASOS Weather Records (USW00024144)
Record envelope, standing records and threshold days for Helena AP ASOS (USW00024144), Montana, United States, with 89 years of record.
Key Facts for Helena AP ASOS
- Helena AP ASOS (USW00024144) is a weather station in Montana, United States at 46.60 latitude and -111.99 longitude, 1,178 m (3,865 ft) above sea level.
- The station reports from 1938 to 2026, 89 years of record.
- 1,464 records set at Helena AP ASOS still stand.
- Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
- Helena AP ASOS set a daily record snow depth of 10.2 cm (4.0 in) on 11 October 2026 (provisional).
Provisional Records
Records set in the last 60 days are provisional until they clear the revision window.
About the Station
- Location: Montana, United States, 46.60 latitude, -111.99 longitude.
- Elevation: 1,178 m (3,865 ft).
- Period of record: 1938 to 2026, 89 years.
- Eligible elements: tmax, tmin, prcp, snow, snwd.
Daily Record Envelope and 2026
12 days at or beyond a record| Month | Highest record high | Lowest record low | 2026 highest maximum | 2026 lowest minimum |
|---|---|---|---|---|
| Jan | 17.2 C (63.0 F) | -41.1 C (-42.0 F) | 14.4 C (57.9 F) | -16.1 C (3.0 F) |
| Feb | 20.6 C (69.1 F) | -41.1 C (-42.0 F) | 16.1 C (61.0 F) | -20.0 C (-4.0 F) |
| Mar | 25.6 C (78.1 F) | -34.4 C (-29.9 F) | 25.0 C (77.0 F) | -15.6 C (3.9 F) |
| Apr | 30.0 C (86.0 F) | -17.2 C (1.0 F) | 27.8 C (82.0 F) | -3.3 C (26.1 F) |
| May | 33.9 C (93.0 F) | -8.3 C (17.1 F) | 32.2 C (90.0 F) | -2.8 C (27.0 F) |
| Jun | 40.0 C (104.0 F) | -1.1 C (30.0 F) | 30.0 C (86.0 F) | 1.1 C (34.0 F) |
| Jul | 40.6 C (105.1 F) | 2.2 C (36.0 F) | 38.9 C (102.0 F) | 8.3 C (46.9 F) |
| Aug | 40.6 C (105.1 F) | -2.2 C (28.0 F) | 39.4 C (102.9 F) | 6.7 C (44.1 F) |
| Sep | 38.9 C (102.0 F) | -7.8 C (18.0 F) | 30.6 C (87.1 F) | 1.1 C (34.0 F) |
| Oct | 31.7 C (89.1 F) | -22.2 C (-8.0 F) | 27.8 C (82.0 F) | -3.9 C (25.0 F) |
| Nov | 24.4 C (75.9 F) | -39.4 C (-38.9 F) | n/a | n/a |
| Dec | 21.1 C (70.0 F) | -38.9 C (-38.0 F) | n/a | n/a |
Which Years Hold Standing Records
1,464 standing records| Year set | Standing records |
|---|---|
| 1938 | 14 |
| 1939 | 26 |
| 1940 | 15 |
| 1941 | 13 |
| 1942 | 21 |
| 1943 | 26 |
| 1944 | 11 |
| 1945 | 10 |
| 1946 | 17 |
| 1947 | 10 |
| 1948 | 11 |
| 1949 | 24 |
| 1950 | 30 |
| 1951 | 35 |
| 1952 | 10 |
| 1953 | 23 |
| 1954 | 30 |
| 1955 | 28 |
| 1956 | 15 |
| 1957 | 21 |
| 1958 | 12 |
| 1959 | 20 |
| 1960 | 19 |
| 1961 | 18 |
| 1962 | 14 |
| 1963 | 16 |
| 1964 | 14 |
| 1965 | 15 |
| 1966 | 18 |
| 1967 | 10 |
| 1968 | 10 |
| 1969 | 21 |
| 1970 | 7 |
| 1971 | 7 |
| 1972 | 34 |
| 1973 | 11 |
| 1974 | 13 |
| 1975 | 15 |
| 1976 | 7 |
| 1977 | 12 |
| 1978 | 10 |
| 1979 | 5 |
| 1980 | 13 |
| 1981 | 7 |
| 1982 | 9 |
| 1983 | 19 |
| 1984 | 16 |
| 1985 | 39 |
| 1986 | 21 |
| 1987 | 20 |
| 1988 | 10 |
| 1989 | 15 |
| 1990 | 18 |
| 1991 | 18 |
| 1992 | 19 |
| 1993 | 10 |
| 1994 | 12 |
| 1995 | 18 |
| 1996 | 19 |
| 1997 | 12 |
| 1998 | 8 |
| 1999 | 17 |
| 2000 | 15 |
| 2001 | 17 |
| 2002 | 23 |
| 2003 | 24 |
| 2004 | 11 |
| 2005 | 12 |
| 2006 | 15 |
| 2007 | 22 |
| 2008 | 15 |
| 2009 | 15 |
| 2010 | 4 |
| 2011 | 9 |
| 2012 | 15 |
| 2013 | 7 |
| 2014 | 15 |
| 2015 | 36 |
| 2016 | 7 |
| 2017 | 11 |
| 2018 | 4 |
| 2019 | 15 |
| 2020 | 18 |
| 2021 | 37 |
| 2022 | 25 |
| 2023 | 20 |
| 2024 | 18 |
| 2025 | 19 |
| 2026 | 17 |
All-Time Record Progression
7 new records| Date | Kind | Detail |
|---|---|---|
| 1969-08-24 | Record high maximum temperature | Record high maximum temperature 40.6 C (105.1 F) |
| 1983-12-24 | Record low maximum temperature | Record low maximum temperature -30.0 C (-22.0 F) |
| 1985-07-11 | Record high minimum temperature | Record high minimum temperature 20.6 C (69.1 F) |
| 1989-02-02 | Record low maximum temperature | Record low maximum temperature -30.6 C (-23.1 F) |
| 2007-07-19 | Record high minimum temperature | Record high minimum temperature 21.1 C (70.0 F) |
| 2007-07-24 | Record high minimum temperature | Record high minimum temperature 21.7 C (71.1 F) |
| 2021-07-28 | Record high minimum temperature | Record high minimum temperature 22.2 C (72.0 F) |
Wettest Day of Each Month
May: 52.3 mm (2.1 in)| Month | Record daily precipitation (mm) | Date |
|---|---|---|
| Jan | 18.0 mm (0.7 in) | 18 January 2012 |
| Feb | 14.7 mm (0.6 in) | 7 February 2024 |
| Mar | 17.8 mm (0.7 in) | 23 March 1945 |
| Apr | 24.9 mm (1.0 in) | 25 April 1975 |
| May | 52.3 mm (2.1 in) | 3 May 1964 |
| Jun | 45.0 mm (1.8 in) | 18 June 1979 |
| Jul | 34.5 mm (1.4 in) | 30 July 1975 |
| Aug | 46.2 mm (1.8 in) | 21 August 1983 |
| Sep | 40.9 mm (1.6 in) | 11 September 1980 |
| Oct | 20.3 mm (0.8 in) | 23 October 1954 |
| Nov | 21.6 mm (0.9 in) | 8 November 2012 |
| Dec | 16.3 mm (0.6 in) | 29 December 2017 |
Period of Record Coverage
1938 to 2026| Year | Days with data | Share of year | Complete |
|---|---|---|---|
| 1938 | 275 | 75% | No |
| 1939 | 365 | 100% | Yes |
| 1940 | 366 | 100% | Yes |
| 1941 | 365 | 100% | Yes |
| 1942 | 365 | 100% | Yes |
| 1943 | 365 | 100% | Yes |
| 1944 | 366 | 100% | Yes |
| 1945 | 365 | 100% | Yes |
| 1946 | 365 | 100% | Yes |
| 1947 | 365 | 100% | Yes |
| 1948 | 366 | 100% | Yes |
| 1949 | 365 | 100% | Yes |
| 1950 | 365 | 100% | Yes |
| 1951 | 365 | 100% | Yes |
| 1952 | 366 | 100% | Yes |
| 1953 | 365 | 100% | Yes |
| 1954 | 365 | 100% | Yes |
| 1955 | 365 | 100% | Yes |
| 1956 | 366 | 100% | Yes |
| 1957 | 365 | 100% | Yes |
| 1958 | 365 | 100% | Yes |
| 1959 | 365 | 100% | Yes |
| 1960 | 366 | 100% | Yes |
| 1961 | 365 | 100% | Yes |
| 1962 | 365 | 100% | Yes |
| 1963 | 365 | 100% | Yes |
| 1964 | 366 | 100% | Yes |
| 1965 | 365 | 100% | Yes |
| 1966 | 365 | 100% | Yes |
| 1967 | 365 | 100% | Yes |
| 1968 | 366 | 100% | Yes |
| 1969 | 365 | 100% | Yes |
| 1970 | 365 | 100% | Yes |
| 1971 | 365 | 100% | Yes |
| 1972 | 366 | 100% | Yes |
| 1973 | 365 | 100% | Yes |
| 1974 | 365 | 100% | Yes |
| 1975 | 365 | 100% | Yes |
| 1976 | 366 | 100% | Yes |
| 1977 | 365 | 100% | Yes |
| 1978 | 365 | 100% | Yes |
| 1979 | 365 | 100% | Yes |
| 1980 | 366 | 100% | Yes |
| 1981 | 365 | 100% | Yes |
| 1982 | 365 | 100% | Yes |
| 1983 | 365 | 100% | Yes |
| 1984 | 366 | 100% | Yes |
| 1985 | 365 | 100% | Yes |
| 1986 | 365 | 100% | Yes |
| 1987 | 365 | 100% | Yes |
| 1988 | 366 | 100% | Yes |
| 1989 | 365 | 100% | Yes |
| 1990 | 365 | 100% | Yes |
| 1991 | 365 | 100% | Yes |
| 1992 | 366 | 100% | Yes |
| 1993 | 365 | 100% | Yes |
| 1994 | 365 | 100% | Yes |
| 1995 | 365 | 100% | Yes |
| 1996 | 365 | 100% | Yes |
| 1997 | 365 | 100% | Yes |
| 1998 | 365 | 100% | Yes |
| 1999 | 365 | 100% | Yes |
| 2000 | 366 | 100% | Yes |
| 2001 | 365 | 100% | Yes |
| 2002 | 365 | 100% | Yes |
| 2003 | 365 | 100% | Yes |
| 2004 | 366 | 100% | Yes |
| 2005 | 365 | 100% | Yes |
| 2006 | 365 | 100% | Yes |
| 2007 | 365 | 100% | Yes |
| 2008 | 366 | 100% | Yes |
| 2009 | 365 | 100% | Yes |
| 2010 | 365 | 100% | Yes |
| 2011 | 365 | 100% | Yes |
| 2012 | 366 | 100% | Yes |
| 2013 | 365 | 100% | Yes |
| 2014 | 365 | 100% | Yes |
| 2015 | 365 | 100% | Yes |
| 2016 | 366 | 100% | Yes |
| 2017 | 365 | 100% | Yes |
| 2018 | 365 | 100% | Yes |
| 2019 | 365 | 100% | Yes |
| 2020 | 366 | 100% | Yes |
| 2021 | 364 | 100% | Yes |
| 2022 | 365 | 100% | Yes |
| 2023 | 365 | 100% | Yes |
| 2024 | 366 | 100% | Yes |
| 2025 | 365 | 100% | Yes |
| 2026 | 286 | 78% | No |
Latest Records
20| Date | Station | Record | Value | Beat old record by | Old record stood | Significance |
|---|---|---|---|---|---|---|
| 11 October 2026 | Helena AP ASOS, US | daily snow depth (Provisional) | 10.2 cm (4.0 in) | 7.2 cm (2.8 in) | 9 years | 21 of 100 (Routine) |
| 10 October 2026 | Helena AP ASOS, US | daily rain (Provisional) | 11.7 mm (0.5 in) | 3.8 mm (0.15 in) | 64 years | 20 of 100 (Routine) |
| 10 October 2026 | Helena AP ASOS, US | daily snowfall (Provisional) | 4.8 cm (1.9 in) | 3.5 cm (1.4 in) | 56 years | 20 of 100 (Routine) |
| 22 August 2026 | Helena AP ASOS, US | daily high min (Provisional) | 16.7 C (62.1 F) | 0.6 C (1.1 F) | 3 years | 9 of 100 (Routine) |
| 21 August 2026 | Helena AP ASOS, US | daily high max (Tie, Provisional) | 35.0 C (95.0 F) | tie | 35 years | 4 of 100 (Routine) |
| 1 August 2026 | Helena AP ASOS, US | daily high max | 39.4 C (102.9 F) | 0.5 C (0.9 F) | 4 years | 10 of 100 (Routine) |
| 25 July 2026 | Helena AP ASOS, US | daily high max | 38.9 C (102.0 F) | 2.2 C (4.0 F) | 20 years | 18 of 100 (Routine) |
| 22 July 2026 | Helena AP ASOS, US | daily high min (Tie) | 18.9 C (66.0 F) | tie | 44 years | 5 of 100 (Routine) |
| 11 July 2026 | Helena AP ASOS, US | daily high max (Tie) | 38.3 C (100.9 F) | tie | 1 year | 2 of 100 (Routine) |
| 29 June 2026 | Helena AP ASOS, US | daily rain | 20.6 mm (0.8 in) | 4.6 mm (0.18 in) | 33 years | 20 of 100 (Routine) |
| 16 June 2026 | Helena AP ASOS, US | daily high min | 15.0 C (59.0 F) | 1.1 C (2.0 F) | 37 years | 22 of 100 (Routine) |
| 30 May 2026 | Helena AP ASOS, US | daily rain | 24.6 mm (1.0 in) | 3.8 mm (0.15 in) | 37 years | 20 of 100 (Routine) |
| 28 May 2026 | Helena AP ASOS, US | daily high min | 13.3 C (55.9 F) | 1.1 C (2.0 F) | 83 years | 35 of 100 (Notable) |
| 26 May 2026 | Helena AP ASOS, US | daily high min | 12.2 C (54.0 F) | 0.5 C (0.9 F) | 68 years | 29 of 100 (Routine) |
| 21 April 2026 | Helena AP ASOS, US | daily high max (Tie) | 27.8 C (82.0 F) | tie | 84 years | 8 of 100 (Routine) |
| 21 March 2026 | Helena AP ASOS, US | daily high min (Tie) | 4.4 C (39.9 F) | tie | 48 years | 5 of 100 (Routine) |
| 20 March 2026 | Helena AP ASOS, US | daily high min | 5.0 C (41.0 F) | 0.6 C (1.1 F) | 80 years | 32 of 100 (Routine) |
| 20 March 2026 | Helena AP ASOS, US | daily high max | 25.0 C (77.0 F) | 4.4 C (7.9 F) | 11 years | 17 of 100 (Routine) |
| 19 March 2026 | Helena AP ASOS, US | daily high max | 22.8 C (73.0 F) | 1.1 C (2.0 F) | 28 years | 17 of 100 (Routine) |
| 14 March 2026 | Helena AP ASOS, US | daily rain | 10.2 mm (0.4 in) | 4.4 mm (0.17 in) | 84 years | 20 of 100 (Routine) |
Climate Trend
87 complete years, 1939 to 2025| Year | Annual mean temperature | Difference from the station mean |
|---|---|---|
| 1939 | 7.6 C | +0.76 C |
| 1940 | 7.4 C | +0.56 C |
| 1941 | 7.1 C | +0.19 C |
| 1942 | 5.5 C | -1.36 C |
| 1943 | 5.2 C | -1.65 C |
| 1944 | 5.6 C | -1.24 C |
| 1945 | 6.5 C | -0.33 C |
| 1946 | 7.1 C | +0.27 C |
| 1947 | 6.6 C | -0.24 C |
| 1948 | 5.6 C | -1.26 C |
| 1949 | 5.2 C | -1.72 C |
| 1950 | 4.9 C | -1.95 C |
| 1951 | 4.4 C | -2.52 C |
| 1952 | 5.8 C | -1.09 C |
| 1953 | 8.2 C | +1.29 C |
| 1954 | 6.3 C | -0.56 C |
| 1955 | 4.6 C | -2.27 C |
| 1956 | 6.4 C | -0.51 C |
| 1957 | 5.8 C | -1.03 C |
| 1958 | 7.0 C | +0.16 C |
| 1959 | 5.7 C | -1.19 C |
| 1960 | 6.4 C | -0.52 C |
| 1961 | 7.6 C | +0.75 C |
| 1962 | 6.7 C | -0.19 C |
| 1963 | 7.2 C | +0.30 C |
| 1964 | 6.1 C | -0.78 C |
| 1965 | 6.5 C | -0.34 C |
| 1966 | 7.7 C | +0.85 C |
| 1967 | 7.4 C | +0.51 C |
| 1968 | 6.0 C | -0.91 C |
| 1969 | 5.2 C | -1.70 C |
| 1970 | 5.7 C | -1.18 C |
| 1971 | 5.5 C | -1.40 C |
| 1972 | 5.1 C | -1.82 C |
| 1973 | 6.3 C | -0.61 C |
| 1974 | 7.1 C | +0.24 C |
| 1975 | 4.7 C | -2.17 C |
| 1976 | 7.0 C | +0.17 C |
| 1977 | 6.7 C | -0.16 C |
| 1978 | 6.2 C | -0.70 C |
| 1979 | 6.2 C | -0.72 C |
| 1980 | 6.7 C | -0.15 C |
| 1981 | 7.9 C | +1.06 C |
| 1982 | 6.1 C | -0.82 C |
| 1983 | 7.0 C | +0.13 C |
| 1984 | 6.8 C | -0.06 C |
| 1985 | 4.8 C | -2.05 C |
| 1986 | 6.7 C | -0.14 C |
| 1987 | 8.0 C | +1.16 C |
| 1988 | 8.1 C | +1.18 C |
| 1989 | 6.0 C | -0.86 C |
| 1990 | 7.5 C | +0.66 C |
| 1991 | 7.5 C | +0.60 C |
| 1992 | 7.7 C | +0.83 C |
| 1993 | 5.3 C | -1.54 C |
| 1994 | 7.7 C | +0.86 C |
| 1995 | 6.3 C | -0.59 C |
| 1996 | 4.6 C | -2.23 C |
| 1997 | 6.3 C | -0.61 C |
| 1998 | 7.3 C | +0.43 C |
| 1999 | 7.5 C | +0.60 C |
| 2000 | 7.1 C | +0.24 C |
| 2001 | 8.3 C | +1.44 C |
| 2002 | 7.3 C | +0.47 C |
| 2003 | 8.5 C | +1.64 C |
| 2004 | 7.7 C | +0.87 C |
| 2005 | 7.4 C | +0.54 C |
| 2006 | 9.0 C | +2.09 C |
| 2007 | 9.1 C | +2.21 C |
| 2008 | 7.5 C | +0.67 C |
| 2009 | 7.1 C | +0.26 C |
| 2010 | 6.5 C | -0.41 C |
| 2011 | 7.1 C | +0.24 C |
| 2012 | 8.5 C | +1.58 C |
| 2013 | 7.9 C | +1.07 C |
| 2014 | 7.7 C | +0.79 C |
| 2015 | 9.1 C | +2.19 C |
| 2016 | 8.8 C | +1.92 C |
| 2017 | 7.5 C | +0.58 C |
| 2018 | 7.1 C | +0.19 C |
| 2019 | 5.9 C | -0.95 C |
| 2020 | 8.6 C | +1.68 C |
| 2021 | 9.0 C | +2.10 C |
| 2022 | 7.6 C | +0.75 C |
| 2023 | 8.7 C | +1.85 C |
| 2024 | 9.1 C | +2.26 C |
| 2025 | 8.5 C | +1.60 C |
The annual mean temperature here has risen by 0.3 C (0.2 to 0.3) per decade over 1939 to 2025. In Fahrenheit: 0.5 F (0.3 to 0.6) per decade. The slope is a straight line fitted to 87 complete years; the brackets give its 95 percent interval.
| Measure | Per decade (C) | Per decade (F) | Period | Complete years | Reading |
|---|---|---|---|---|---|
| Annual mean temperature | 0.3 C (0.2 to 0.3) per decade | 0.5 F (0.3 to 0.6) per decade | 1939 to 2025 | 87 | Rise |
| Mean daily maximum | 0.2 C (0.1 to 0.3) per decade | 0.4 F (0.3 to 0.6) per decade | 1939 to 2025 | 87 | Rise |
| Mean daily minimum | 0.3 C (0.2 to 0.4) per decade | 0.5 F (0.4 to 0.7) per decade | 1939 to 2025 | 87 | Rise |
A year is complete when all 12 months have at least 20 days of both daily maximum and daily minimum readings. The annual mean is the mean of the monthly means. The trend describes this one station over this period; it does not say what caused the change.
Extremes by Year
1938 to 2026| Measure | Record | Year of the record | Median year | Years with a value |
|---|---|---|---|---|
| Hottest day (TXx) | 40.6 C (105.1 F) | 1969 | 36.7 C (98.1 F) | 89 |
| Coldest night (TNn) | -41.1 C (-42.0 F) | 1957 | -31.1 C (-24.0 F) | 89 |
| Wettest day (Rx1day) | 52.3 mm (2.1 in) | 1964 | 24.1 mm (0.9 in) | 89 |
| Wettest five days (Rx5day) | 97.8 mm (3.9 in) | 1981 | 39.4 mm (1.6 in) | 89 |
| Longest dry spell (CDD) | 71 days | 1987 | 35 days | 89 |
Hottest day (TXx)
| Year | Hottest day (TXx) |
|---|---|
| 1938 | 35.0 C (95.0 F) |
| 1939 | 37.8 C (100.0 F) |
| 1940 | 39.4 C (102.9 F) |
| 1941 | 36.7 C (98.1 F) |
| 1942 | 36.1 C (97.0 F) |
| 1943 | 35.6 C (96.1 F) |
| 1944 | 33.3 C (91.9 F) |
| 1945 | 35.6 C (96.1 F) |
| 1946 | 36.7 C (98.1 F) |
| 1947 | 36.1 C (97.0 F) |
| 1948 | 34.4 C (93.9 F) |
| 1949 | 38.9 C (102.0 F) |
| 1950 | 35.6 C (96.1 F) |
| 1951 | 36.7 C (98.1 F) |
| 1952 | 35.6 C (96.1 F) |
| 1953 | 37.2 C (99.0 F) |
| 1954 | 36.1 C (97.0 F) |
| 1955 | 35.6 C (96.1 F) |
| 1956 | 35.0 C (95.0 F) |
| 1957 | 36.1 C (97.0 F) |
| 1958 | 35.0 C (95.0 F) |
| 1959 | 36.1 C (97.0 F) |
| 1960 | 38.9 C (102.0 F) |
| 1961 | 39.4 C (102.9 F) |
| 1962 | 35.6 C (96.1 F) |
| 1963 | 36.7 C (98.1 F) |
| 1964 | 35.0 C (95.0 F) |
| 1965 | 35.0 C (95.0 F) |
| 1966 | 37.8 C (100.0 F) |
| 1967 | 37.2 C (99.0 F) |
| 1968 | 35.0 C (95.0 F) |
| 1969 | 40.6 C (105.1 F) |
| 1970 | 36.7 C (98.1 F) |
| 1971 | 34.4 C (93.9 F) |
| 1972 | 33.9 C (93.0 F) |
| 1973 | 38.9 C (102.0 F) |
| 1974 | 35.6 C (96.1 F) |
| 1975 | 35.6 C (96.1 F) |
| 1976 | 35.0 C (95.0 F) |
| 1977 | 33.9 C (93.0 F) |
| 1978 | 35.0 C (95.0 F) |
| 1979 | 36.7 C (98.1 F) |
| 1980 | 34.4 C (93.9 F) |
| 1981 | 38.9 C (102.0 F) |
| 1982 | 34.4 C (93.9 F) |
| 1983 | 37.8 C (100.0 F) |
| 1984 | 37.2 C (99.0 F) |
| 1985 | 38.3 C (100.9 F) |
| 1986 | 37.2 C (99.0 F) |
| 1987 | 36.1 C (97.0 F) |
| 1988 | 37.8 C (100.0 F) |
| 1989 | 36.7 C (98.1 F) |
| 1990 | 39.4 C (102.9 F) |
| 1991 | 36.7 C (98.1 F) |
| 1992 | 36.7 C (98.1 F) |
| 1993 | 35.0 C (95.0 F) |
| 1994 | 36.7 C (98.1 F) |
| 1995 | 36.7 C (98.1 F) |
| 1996 | 36.1 C (97.0 F) |
| 1997 | 34.4 C (93.9 F) |
| 1998 | 36.1 C (97.0 F) |
| 1999 | 37.8 C (100.0 F) |
| 2000 | 38.3 C (100.9 F) |
| 2001 | 38.9 C (102.0 F) |
| 2002 | 40.6 C (105.1 F) |
| 2003 | 40.0 C (104.0 F) |
| 2004 | 37.2 C (99.0 F) |
| 2005 | 37.8 C (100.0 F) |
| 2006 | 38.9 C (102.0 F) |
| 2007 | 38.9 C (102.0 F) |
| 2008 | 37.2 C (99.0 F) |
| 2009 | 37.2 C (99.0 F) |
| 2010 | 36.1 C (97.0 F) |
| 2011 | 37.2 C (99.0 F) |
| 2012 | 36.7 C (98.1 F) |
| 2013 | 37.8 C (100.0 F) |
| 2014 | 35.6 C (96.1 F) |
| 2015 | 39.4 C (102.9 F) |
| 2016 | 37.2 C (99.0 F) |
| 2017 | 38.9 C (102.0 F) |
| 2018 | 37.8 C (100.0 F) |
| 2019 | 35.6 C (96.1 F) |
| 2020 | 37.8 C (100.0 F) |
| 2021 | 40.0 C (104.0 F) |
| 2022 | 38.9 C (102.0 F) |
| 2023 | 39.4 C (102.9 F) |
| 2024 | 39.4 C (102.9 F) |
| 2025 | 36.1 C (97.0 F) |
| 2026 | 39.4 C (102.9 F) |
Coldest night (TNn)
| Year | Coldest night (TNn) |
|---|---|
| 1938 | -25.6 C (-14.1 F) |
| 1939 | -37.8 C (-36.0 F) |
| 1940 | -28.9 C (-20.0 F) |
| 1941 | -33.9 C (-29.0 F) |
| 1942 | -38.3 C (-36.9 F) |
| 1943 | -36.1 C (-33.0 F) |
| 1944 | -32.2 C (-26.0 F) |
| 1945 | -31.1 C (-24.0 F) |
| 1946 | -27.8 C (-18.0 F) |
| 1947 | -27.8 C (-18.0 F) |
| 1948 | -30.0 C (-22.0 F) |
| 1949 | -36.7 C (-34.1 F) |
| 1950 | -35.0 C (-31.0 F) |
| 1951 | -32.8 C (-27.0 F) |
| 1952 | -31.1 C (-24.0 F) |
| 1953 | -21.7 C (-7.1 F) |
| 1954 | -37.8 C (-36.0 F) |
| 1955 | -34.4 C (-29.9 F) |
| 1956 | -35.0 C (-31.0 F) |
| 1957 | -41.1 C (-42.0 F) |
| 1958 | -23.9 C (-11.0 F) |
| 1959 | -39.4 C (-38.9 F) |
| 1960 | -31.1 C (-24.0 F) |
| 1961 | -30.0 C (-22.0 F) |
| 1962 | -35.6 C (-32.1 F) |
| 1963 | -33.3 C (-27.9 F) |
| 1964 | -38.9 C (-38.0 F) |
| 1965 | -26.7 C (-16.1 F) |
| 1966 | -23.3 C (-9.9 F) |
| 1967 | -32.2 C (-26.0 F) |
| 1968 | -38.3 C (-36.9 F) |
| 1969 | -37.2 C (-35.0 F) |
| 1970 | -28.3 C (-18.9 F) |
| 1971 | -34.4 C (-29.9 F) |
| 1972 | -37.2 C (-35.0 F) |
| 1973 | -31.1 C (-24.0 F) |
| 1974 | -34.4 C (-29.9 F) |
| 1975 | -31.1 C (-24.0 F) |
| 1976 | -28.9 C (-20.0 F) |
| 1977 | -28.9 C (-20.0 F) |
| 1978 | -35.0 C (-31.0 F) |
| 1979 | -31.7 C (-25.1 F) |
| 1980 | -31.7 C (-25.1 F) |
| 1981 | -33.3 C (-27.9 F) |
| 1982 | -29.4 C (-20.9 F) |
| 1983 | -38.3 C (-36.9 F) |
| 1984 | -28.3 C (-18.9 F) |
| 1985 | -32.8 C (-27.0 F) |
| 1986 | -31.1 C (-24.0 F) |
| 1987 | -24.4 C (-11.9 F) |
| 1988 | -26.7 C (-16.1 F) |
| 1989 | -36.1 C (-33.0 F) |
| 1990 | -37.2 C (-35.0 F) |
| 1991 | -28.3 C (-18.9 F) |
| 1992 | -29.4 C (-20.9 F) |
| 1993 | -30.6 C (-23.1 F) |
| 1994 | -32.8 C (-27.0 F) |
| 1995 | -29.4 C (-20.9 F) |
| 1996 | -41.1 C (-42.0 F) |
| 1997 | -36.1 C (-33.0 F) |
| 1998 | -33.9 C (-29.0 F) |
| 1999 | -23.3 C (-9.9 F) |
| 2000 | -27.8 C (-18.0 F) |
| 2001 | -22.8 C (-9.0 F) |
| 2002 | -25.0 C (-13.0 F) |
| 2003 | -25.0 C (-13.0 F) |
| 2004 | -35.6 C (-32.1 F) |
| 2005 | -31.7 C (-25.1 F) |
| 2006 | -26.1 C (-15.0 F) |
| 2007 | -23.9 C (-11.0 F) |
| 2008 | -27.8 C (-18.0 F) |
| 2009 | -30.6 C (-23.1 F) |
| 2010 | -28.9 C (-20.0 F) |
| 2011 | -28.3 C (-18.9 F) |
| 2012 | -22.8 C (-9.0 F) |
| 2013 | -27.1 C (-16.8 F) |
| 2014 | -32.2 C (-26.0 F) |
| 2015 | -21.0 C (-5.8 F) |
| 2016 | -33.2 C (-27.8 F) |
| 2017 | -26.6 C (-15.9 F) |
| 2018 | -27.1 C (-16.8 F) |
| 2019 | -34.3 C (-29.7 F) |
| 2020 | -21.6 C (-6.9 F) |
| 2021 | -30.5 C (-22.9 F) |
| 2022 | -37.1 C (-34.8 F) |
| 2023 | -24.9 C (-12.8 F) |
| 2024 | -37.7 C (-35.9 F) |
| 2025 | -31.0 C (-23.8 F) |
| 2026 | -20.0 C (-4.0 F) |
Wettest day (Rx1day)
| Year | Wettest day (Rx1day) |
|---|---|
| 1938 | 20.6 mm (0.8 in) |
| 1939 | 16.3 mm (0.6 in) |
| 1940 | 16.5 mm (0.6 in) |
| 1941 | 25.4 mm (1.0 in) |
| 1942 | 19.3 mm (0.8 in) |
| 1943 | 30.5 mm (1.2 in) |
| 1944 | 27.9 mm (1.1 in) |
| 1945 | 20.3 mm (0.8 in) |
| 1946 | 18.5 mm (0.7 in) |
| 1947 | 39.4 mm (1.6 in) |
| 1948 | 25.7 mm (1.0 in) |
| 1949 | 15.5 mm (0.6 in) |
| 1950 | 19.6 mm (0.8 in) |
| 1951 | 24.1 mm (0.9 in) |
| 1952 | 17.0 mm (0.7 in) |
| 1953 | 39.6 mm (1.6 in) |
| 1954 | 21.3 mm (0.8 in) |
| 1955 | 24.9 mm (1.0 in) |
| 1956 | 16.0 mm (0.6 in) |
| 1957 | 45.2 mm (1.8 in) |
| 1958 | 24.9 mm (1.0 in) |
| 1959 | 15.5 mm (0.6 in) |
| 1960 | 17.0 mm (0.7 in) |
| 1961 | 11.2 mm (0.4 in) |
| 1962 | 33.5 mm (1.3 in) |
| 1963 | 14.7 mm (0.6 in) |
| 1964 | 52.3 mm (2.1 in) |
| 1965 | 27.4 mm (1.1 in) |
| 1966 | 10.2 mm (0.4 in) |
| 1967 | 28.2 mm (1.1 in) |
| 1968 | 23.1 mm (0.9 in) |
| 1969 | 27.2 mm (1.1 in) |
| 1970 | 25.7 mm (1.0 in) |
| 1971 | 14.5 mm (0.6 in) |
| 1972 | 15.7 mm (0.6 in) |
| 1973 | 14.0 mm (0.6 in) |
| 1974 | 29.2 mm (1.1 in) |
| 1975 | 34.5 mm (1.4 in) |
| 1976 | 27.4 mm (1.1 in) |
| 1977 | 27.2 mm (1.1 in) |
| 1978 | 16.3 mm (0.6 in) |
| 1979 | 45.0 mm (1.8 in) |
| 1980 | 40.9 mm (1.6 in) |
| 1981 | 49.0 mm (1.9 in) |
| 1982 | 39.4 mm (1.6 in) |
| 1983 | 46.2 mm (1.8 in) |
| 1984 | 24.9 mm (1.0 in) |
| 1985 | 18.3 mm (0.7 in) |
| 1986 | 26.9 mm (1.1 in) |
| 1987 | 20.8 mm (0.8 in) |
| 1988 | 21.8 mm (0.9 in) |
| 1989 | 20.1 mm (0.8 in) |
| 1990 | 20.3 mm (0.8 in) |
| 1991 | 22.9 mm (0.9 in) |
| 1992 | 17.0 mm (0.7 in) |
| 1993 | 22.4 mm (0.9 in) |
| 1994 | 9.4 mm (0.37 in) |
| 1995 | 23.9 mm (0.9 in) |
| 1996 | 16.0 mm (0.6 in) |
| 1997 | 18.8 mm (0.7 in) |
| 1998 | 31.2 mm (1.2 in) |
| 1999 | 22.9 mm (0.9 in) |
| 2000 | 20.1 mm (0.8 in) |
| 2001 | 29.2 mm (1.1 in) |
| 2002 | 26.4 mm (1.0 in) |
| 2003 | 16.3 mm (0.6 in) |
| 2004 | 26.9 mm (1.1 in) |
| 2005 | 37.1 mm (1.5 in) |
| 2006 | 29.5 mm (1.2 in) |
| 2007 | 33.5 mm (1.3 in) |
| 2008 | 18.0 mm (0.7 in) |
| 2009 | 28.4 mm (1.1 in) |
| 2010 | 29.2 mm (1.1 in) |
| 2011 | 29.0 mm (1.1 in) |
| 2012 | 21.6 mm (0.9 in) |
| 2013 | 22.4 mm (0.9 in) |
| 2014 | 29.5 mm (1.2 in) |
| 2015 | 21.8 mm (0.9 in) |
| 2016 | 13.2 mm (0.5 in) |
| 2017 | 25.9 mm (1.0 in) |
| 2018 | 24.1 mm (0.9 in) |
| 2019 | 28.2 mm (1.1 in) |
| 2020 | 19.0 mm (0.7 in) |
| 2021 | 18.8 mm (0.7 in) |
| 2022 | 27.7 mm (1.1 in) |
| 2023 | 32.0 mm (1.3 in) |
| 2024 | 24.9 mm (1.0 in) |
| 2025 | 25.1 mm (1.0 in) |
| 2026 | 24.6 mm (1.0 in) |
Wettest five days (Rx5day)
| Year | Wettest five days (Rx5day) |
|---|---|
| 1938 | 47.7 mm (1.9 in) |
| 1939 | 28.1 mm (1.1 in) |
| 1940 | 31.0 mm (1.2 in) |
| 1941 | 39.1 mm (1.5 in) |
| 1942 | 25.4 mm (1.0 in) |
| 1943 | 43.5 mm (1.7 in) |
| 1944 | 40.7 mm (1.6 in) |
| 1945 | 40.7 mm (1.6 in) |
| 1946 | 36.3 mm (1.4 in) |
| 1947 | 66.4 mm (2.6 in) |
| 1948 | 52.7 mm (2.1 in) |
| 1949 | 28.7 mm (1.1 in) |
| 1950 | 32.5 mm (1.3 in) |
| 1951 | 32.0 mm (1.3 in) |
| 1952 | 26.9 mm (1.1 in) |
| 1953 | 51.8 mm (2.0 in) |
| 1954 | 35.6 mm (1.4 in) |
| 1955 | 36.0 mm (1.4 in) |
| 1956 | 28.5 mm (1.1 in) |
| 1957 | 61.5 mm (2.4 in) |
| 1958 | 48.2 mm (1.9 in) |
| 1959 | 32.6 mm (1.3 in) |
| 1960 | 28.9 mm (1.1 in) |
| 1961 | 24.7 mm (1.0 in) |
| 1962 | 49.8 mm (2.0 in) |
| 1963 | 23.6 mm (0.9 in) |
| 1964 | 84.1 mm (3.3 in) |
| 1965 | 58.4 mm (2.3 in) |
| 1966 | 13.2 mm (0.5 in) |
| 1967 | 33.1 mm (1.3 in) |
| 1968 | 43.7 mm (1.7 in) |
| 1969 | 57.9 mm (2.3 in) |
| 1970 | 31.8 mm (1.3 in) |
| 1971 | 26.8 mm (1.1 in) |
| 1972 | 18.0 mm (0.7 in) |
| 1973 | 18.9 mm (0.7 in) |
| 1974 | 47.2 mm (1.9 in) |
| 1975 | 50.2 mm (2.0 in) |
| 1976 | 32.0 mm (1.3 in) |
| 1977 | 35.1 mm (1.4 in) |
| 1978 | 43.0 mm (1.7 in) |
| 1979 | 48.8 mm (1.9 in) |
| 1980 | 52.9 mm (2.1 in) |
| 1981 | 97.8 mm (3.9 in) |
| 1982 | 44.5 mm (1.8 in) |
| 1983 | 60.5 mm (2.4 in) |
| 1984 | 28.8 mm (1.1 in) |
| 1985 | 43.9 mm (1.7 in) |
| 1986 | 35.3 mm (1.4 in) |
| 1987 | 40.3 mm (1.6 in) |
| 1988 | 30.2 mm (1.2 in) |
| 1989 | 25.9 mm (1.0 in) |
| 1990 | 31.7 mm (1.2 in) |
| 1991 | 38.1 mm (1.5 in) |
| 1992 | 35.5 mm (1.4 in) |
| 1993 | 39.4 mm (1.6 in) |
| 1994 | 21.0 mm (0.8 in) |
| 1995 | 47.3 mm (1.9 in) |
| 1996 | 21.9 mm (0.9 in) |
| 1997 | 40.9 mm (1.6 in) |
| 1998 | 41.1 mm (1.6 in) |
| 1999 | 44.2 mm (1.7 in) |
| 2000 | 39.4 mm (1.6 in) |
| 2001 | 34.5 mm (1.4 in) |
| 2002 | 69.9 mm (2.8 in) |
| 2003 | 22.1 mm (0.9 in) |
| 2004 | 40.0 mm (1.6 in) |
| 2005 | 49.3 mm (1.9 in) |
| 2006 | 57.1 mm (2.2 in) |
| 2007 | 49.3 mm (1.9 in) |
| 2008 | 52.3 mm (2.1 in) |
| 2009 | 36.6 mm (1.4 in) |
| 2010 | 44.2 mm (1.7 in) |
| 2011 | 72.2 mm (2.8 in) |
| 2012 | 36.3 mm (1.4 in) |
| 2013 | 30.7 mm (1.2 in) |
| 2014 | 43.3 mm (1.7 in) |
| 2015 | 27.7 mm (1.1 in) |
| 2016 | 21.4 mm (0.8 in) |
| 2017 | 43.4 mm (1.7 in) |
| 2018 | 53.6 mm (2.1 in) |
| 2019 | 53.9 mm (2.1 in) |
| 2020 | 34.5 mm (1.4 in) |
| 2021 | 42.3 mm (1.7 in) |
| 2022 | 45.0 mm (1.8 in) |
| 2023 | 37.1 mm (1.5 in) |
| 2024 | 28.3 mm (1.1 in) |
| 2025 | 44.6 mm (1.8 in) |
| 2026 | 49.3 mm (1.9 in) |
Longest dry spell (CDD)
| Year | Longest dry spell (CDD) |
|---|---|
| 1938 | 34 days |
| 1939 | 44 days |
| 1940 | 40 days |
| 1941 | 40 days |
| 1942 | 33 days |
| 1943 | 31 days |
| 1944 | 39 days |
| 1945 | 44 days |
| 1946 | 23 days |
| 1947 | 26 days |
| 1948 | 35 days |
| 1949 | 36 days |
| 1950 | 26 days |
| 1951 | 24 days |
| 1952 | 30 days |
| 1953 | 48 days |
| 1954 | 34 days |
| 1955 | 37 days |
| 1956 | 27 days |
| 1957 | 22 days |
| 1958 | 29 days |
| 1959 | 49 days |
| 1960 | 35 days |
| 1961 | 54 days |
| 1962 | 25 days |
| 1963 | 14 days |
| 1964 | 64 days |
| 1965 | 31 days |
| 1966 | 24 days |
| 1967 | 21 days |
| 1968 | 24 days |
| 1969 | 53 days |
| 1970 | 39 days |
| 1971 | 22 days |
| 1972 | 48 days |
| 1973 | 58 days |
| 1974 | 27 days |
| 1975 | 32 days |
| 1976 | 62 days |
| 1977 | 25 days |
| 1978 | 57 days |
| 1979 | 51 days |
| 1980 | 34 days |
| 1981 | 32 days |
| 1982 | 31 days |
| 1983 | 49 days |
| 1984 | 32 days |
| 1985 | 40 days |
| 1986 | 35 days |
| 1987 | 71 days |
| 1988 | 60 days |
| 1989 | 30 days |
| 1990 | 43 days |
| 1991 | 37 days |
| 1992 | 41 days |
| 1993 | 23 days |
| 1994 | 30 days |
| 1995 | 30 days |
| 1996 | 53 days |
| 1997 | 71 days |
| 1998 | 33 days |
| 1999 | 36 days |
| 2000 | 28 days |
| 2001 | 33 days |
| 2002 | 44 days |
| 2003 | 35 days |
| 2004 | 48 days |
| 2005 | 38 days |
| 2006 | 34 days |
| 2007 | 38 days |
| 2008 | 29 days |
| 2009 | 43 days |
| 2010 | 25 days |
| 2011 | 31 days |
| 2012 | 36 days |
| 2013 | 51 days |
| 2014 | 25 days |
| 2015 | 30 days |
| 2016 | 37 days |
| 2017 | 66 days |
| 2018 | 49 days |
| 2019 | 23 days |
| 2020 | 39 days |
| 2021 | 50 days |
| 2022 | 34 days |
| 2023 | 65 days |
| 2024 | 47 days |
| 2025 | 27 days |
| 2026 | 35 days |
Each chart shows one value per year; the dot marks the record year. TXx is the hottest daily maximum, TNn the coldest daily minimum, Rx1day and Rx5day the largest one-day and five-day rain totals, and CDD the longest run of days with less than 1 mm of rain. A year with missing days can understate an extreme.
Frost Dates and Growing Season
87 years with a frostAcross 87 years with a frost, the median last spring frost at Helena AP ASOS falls on 16 May and the median first autumn frost on 21 September, which leaves a median of 128 days between them.
In 1996 to 2025 the median growing season was 144 days. That is 21 days more than in 1939 to 1968.
Fitted over all years, the growing season changes by +3.4 days per decade at this station.
| Measure | Median, all years | Earliest period (1939 to 1968) | Recent period (1996 to 2025) | Recent against earliest | Fitted trend |
|---|---|---|---|---|---|
| Last spring frost | 16 May | 19 May | 11 May | 8 days earlier | -1.1 days per decade |
| First autumn frost | 21 September | 17 September | 2 October | 15 days later | +2.3 days per decade |
| Growing days | 128 days | 123 days | 144 days | 21 days more | +3.4 days per decade |
A frost day is a day with a daily minimum at or below 0 C (32 F). The last spring frost and the first autumn frost are the last and first such days of the cold season, and growing days are the days between them. A negative trend for the last spring frost means it comes earlier.
Rainfall Return Levels
86 years, 1940 to 2025A day with at least 23.6 mm (0.9 in) of rain is expected about once in 2 years. A day with at least 52.5 mm (2.1 in) of rain is expected about once in 100 years.
| Expected about once in | A day with at least | Note |
|---|---|---|
| 2 years | 23.6 mm (0.9 in) | |
| 5 years | 31.5 mm (1.2 in) | |
| 10 years | 36.7 mm (1.4 in) | |
| 25 years | 43.1 mm (1.7 in) | |
| 50 years | 47.9 mm (1.9 in) | |
| 100 years | 52.5 mm (2.1 in) | Longer than the 86 years of record |
The levels come from a generalised extreme value (GEV) distribution fitted by L-moments to the wettest-day total of each year, 86 years of values from 1940 to 2025.
A return level is an estimate. It is least reliable for the long periods, 50 and 100 years, and for any period longer than the record behind the fit, where the fit has to reach past the largest day actually observed. It is not a forecast.
The largest wettest-day totals in the fit: 52.3 mm (2.1 in) in 1964; 49.0 mm (1.9 in) in 1981; 46.2 mm (1.8 in) in 1983.
Station Changes
1 suspectedOne change was suspected in the annual mean temperature of Helena AP ASOS, at 2000. Each is measured against neighbouring stations.
- Relative to 5 neighbouring stations, the station's annual mean temperature from 2000 ran 0.5 C (0.9 F) higher than in the years before (likely change).
| Year | Shift (C) | Shift (F) | Strength | Neighbours |
|---|---|---|---|---|
| 2000 | +0.5 | +0.9 | likely | 5 |
Possible change at the station (a move, a new instrument or a new site); the record is kept as measured. A "likely" change has a larger test statistic than a "possible" one. Neither says why the station differs from its neighbours. How changes are found, and the largest ones.
Climate Twins
2011 to 2025 against 1961 to 1990Over 2011 to 2025, Helena AP ASOS had a mean temperature of 8.1 C (46.5 F) and 292.2 mm (11.5 in) of rain a year. The 3 stations whose 1961 to 1990 climate was closest to that are Thiokol Propulsion F S (United States, 544 km away), Dull Ctr 1SE (United States, 656 km away) and Midwest (United States, 572 km away).
| Twin station | Country | Distance away | Mean temperature, 1961-1990 | Rain a year, 1961-1990 | Climate difference |
|---|---|---|---|---|---|
| Thiokol Propulsion F S | United States | 544 km (338 mi) | 8.2 C (46.8 F) | 364.0 mm (14.3 in) | 0.79 |
| Dull Ctr 1SE | United States | 656 km (408 mi) | 8.1 C (46.7 F) | 304.5 mm (12.0 in) | 0.84 |
| Midwest | United States | 572 km (355 mi) | 8.4 C (47.1 F) | 335.1 mm (13.2 in) | 0.85 |
Twins are stations, not cities. A twin is one of the three stations at least 100 km away whose earlier climate is closest to this station's recent one, so a close match does not mean the two places look alike in other ways. A station move or a gap in a record can change that station's averages. The list describes past climate; it is not a forecast and does not say what caused any change. How twins are found, and a search for any station.
Download the Data
Source: NOAA National Centers for Environmental Information, Global Historical Climatology Network Daily (GHCN-Daily). Records are computed by World Extreme Weather Monitor and are not official NOAA products. (US Government open data (NOAA NCEI)) Data as of 2026-10-16 (16 October 2026). Records are computed by this site and are not official.
Data as of . Last revised (2026-10-16).