Heart Butte Dam Weather Records (USC00324091)
Record envelope, standing records and threshold days for Heart Butte Dam (USC00324091), North Dakota, United States, with 43 years of record.
Key Facts for Heart Butte Dam
- Heart Butte Dam (USC00324091) is a weather station in North Dakota, United States at 46.59 latitude and -101.81 longitude, 650 m (2,134 ft) above sea level.
- The station reports from 1984 to 2026, 43 years of record.
- 1,464 records set at Heart Butte Dam still stand.
- Records are tracked for tmax, tmin, prcp: an element needs 30 years of data to be eligible.
- Heart Butte Dam set a daily record high minimum temperature of 13.9 C (57.0 F) on 29 September 2026 (provisional).
Provisional Records
Records set in the last 60 days are provisional until they clear the revision window.
About the Station
- Location: North Dakota, United States, 46.59 latitude, -101.81 longitude.
- Elevation: 650 m (2,134 ft).
- Period of record: 1984 to 2026, 43 years.
- Eligible elements: tmax, tmin, prcp.
Daily Record Envelope and 2026
8 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) | -38.9 C (-38.0 F) | 9.4 C (48.9 F) | -28.9 C (-20.0 F) |
| Feb | 19.4 C (66.9 F) | -41.1 C (-42.0 F) | 9.4 C (48.9 F) | -21.1 C (-6.0 F) |
| Mar | 28.9 C (84.0 F) | -35.0 C (-31.0 F) | 22.8 C (73.0 F) | -21.7 C (-7.1 F) |
| Apr | 34.4 C (93.9 F) | -20.0 C (-4.0 F) | 28.9 C (84.0 F) | -8.3 C (17.1 F) |
| May | 35.0 C (95.0 F) | -8.3 C (17.1 F) | 32.2 C (90.0 F) | -6.1 C (21.0 F) |
| Jun | 43.3 C (109.9 F) | 0.0 C (32.0 F) | 32.2 C (90.0 F) | 5.6 C (42.1 F) |
| Jul | 43.9 C (111.0 F) | 5.0 C (41.0 F) | 41.1 C (106.0 F) | 12.2 C (54.0 F) |
| Aug | 40.6 C (105.1 F) | 0.6 C (33.1 F) | 37.2 C (99.0 F) | 6.1 C (43.0 F) |
| Sep | 38.9 C (102.0 F) | -8.9 C (16.0 F) | 33.9 C (93.0 F) | 4.4 C (39.9 F) |
| Oct | 36.1 C (97.0 F) | -19.4 C (-2.9 F) | 27.8 C (82.0 F) | -0.6 C (30.9 F) |
| Nov | 28.3 C (82.9 F) | -33.3 C (-27.9 F) | n/a | n/a |
| Dec | 19.4 C (66.9 F) | -38.3 C (-36.9 F) | n/a | n/a |
Which Years Hold Standing Records
1,464 standing records| Year set | Standing records |
|---|---|
| 1984 | 18 |
| 1985 | 63 |
| 1986 | 34 |
| 1987 | 41 |
| 1988 | 62 |
| 1989 | 56 |
| 1990 | 36 |
| 1991 | 59 |
| 1992 | 60 |
| 1993 | 34 |
| 1994 | 36 |
| 1995 | 35 |
| 1996 | 56 |
| 1997 | 43 |
| 1998 | 26 |
| 1999 | 24 |
| 2000 | 34 |
| 2001 | 30 |
| 2002 | 42 |
| 2003 | 50 |
| 2004 | 35 |
| 2005 | 44 |
| 2006 | 32 |
| 2007 | 27 |
| 2008 | 16 |
| 2009 | 34 |
| 2010 | 15 |
| 2011 | 22 |
| 2012 | 38 |
| 2013 | 26 |
| 2014 | 29 |
| 2015 | 33 |
| 2016 | 22 |
| 2017 | 31 |
| 2018 | 21 |
| 2019 | 17 |
| 2020 | 33 |
| 2021 | 31 |
| 2022 | 22 |
| 2023 | 31 |
| 2024 | 29 |
| 2025 | 27 |
| 2026 | 10 |
All-Time Record Progression
1 new records| Date | Kind | Detail |
|---|---|---|
| 2025-02-19 | Record low minimum temperature | Record low minimum temperature -41.1 C (-42.0 F) |
Wettest Day of Each Month
Jul: 114.8 mm (4.5 in)| Month | Record daily precipitation (mm) | Date |
|---|---|---|
| Jan | 17.0 mm (0.7 in) | 12 January 1988 |
| Feb | 20.1 mm (0.8 in) | 26 February 2000 |
| Mar | 23.1 mm (0.9 in) | 24 March 1996 |
| Apr | 62.7 mm (2.5 in) | 5 April 1997 |
| May | 77.5 mm (3.1 in) | 21 May 2011 |
| Jun | 50.8 mm (2.0 in) | 13 June 2011 |
| Jul | 114.8 mm (4.5 in) | 27 July 2001 |
| Aug | 61.0 mm (2.4 in) | 12 August 1999 |
| Sep | 46.7 mm (1.8 in) | 16 September 1994 |
| Oct | 53.8 mm (2.1 in) | 5 October 1998 |
| Nov | 29.0 mm (1.1 in) | 8 November 1986 |
| Dec | 17.8 mm (0.7 in) | 26 December 1988 |
Period of Record Coverage
1984 to 2026| Year | Days with data | Share of year | Complete |
|---|---|---|---|
| 1984 | 114 | 31% | No |
| 1985 | 352 | 96% | Yes |
| 1986 | 358 | 98% | Yes |
| 1987 | 364 | 100% | Yes |
| 1988 | 366 | 100% | Yes |
| 1989 | 364 | 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 | 366 | 100% | Yes |
| 1997 | 365 | 100% | Yes |
| 1998 | 365 | 100% | Yes |
| 1999 | 365 | 100% | Yes |
| 2000 | 365 | 100% | Yes |
| 2001 | 365 | 100% | Yes |
| 2002 | 353 | 97% | Yes |
| 2003 | 365 | 100% | Yes |
| 2004 | 366 | 100% | Yes |
| 2005 | 365 | 100% | Yes |
| 2006 | 365 | 100% | Yes |
| 2007 | 362 | 99% | Yes |
| 2008 | 364 | 99% | Yes |
| 2009 | 365 | 100% | Yes |
| 2010 | 351 | 96% | Yes |
| 2011 | 348 | 95% | Yes |
| 2012 | 348 | 95% | Yes |
| 2013 | 353 | 97% | Yes |
| 2014 | 342 | 94% | Yes |
| 2015 | 341 | 93% | Yes |
| 2016 | 351 | 96% | Yes |
| 2017 | 347 | 95% | Yes |
| 2018 | 350 | 96% | Yes |
| 2019 | 350 | 96% | Yes |
| 2020 | 362 | 99% | Yes |
| 2021 | 355 | 97% | Yes |
| 2022 | 334 | 92% | Yes |
| 2023 | 329 | 90% | Yes |
| 2024 | 325 | 89% | No |
| 2025 | 213 | 58% | No |
| 2026 | 145 | 40% | No |
Latest Records
20| Date | Station | Record | Value | Beat old record by | Old record stood | Significance |
|---|---|---|---|---|---|---|
| 29 September 2026 | Heart Butte Dam, US | daily high min (Provisional) | 13.9 C (57.0 F) | 1.7 C (3.1 F) | 28 years | 15 of 100 (Routine) |
| 23 September 2026 | Heart Butte Dam, US | daily high min (Provisional) | 11.1 C (52.0 F) | 0.5 C (0.9 F) | 19 years | 10 of 100 (Routine) |
| 15 August 2026 | Heart Butte Dam, US | daily rain | 24.1 mm (0.9 in) | 11.1 mm (0.4 in) | 1 year | 15 of 100 (Routine) |
| 3 August 2026 | Heart Butte Dam, US | daily high min | 18.9 C (66.0 F) | 0.6 C (1.1 F) | 1 year | 5 of 100 (Routine) |
| 20 July 2026 | Heart Butte Dam, US | daily high max | 38.3 C (100.9 F) | 1.6 C (2.9 F) | 21 years | 13 of 100 (Routine) |
| 15 July 2026 | Heart Butte Dam, US | daily high min (Tie) | 19.4 C (66.9 F) | tie | 24 years | 2 of 100 (Routine) |
| 14 July 2026 | Heart Butte Dam, US | daily high max | 40.6 C (105.1 F) | 3.4 C (6.1 F) | 24 years | 18 of 100 (Routine) |
| 13 July 2026 | Heart Butte Dam, US | daily high min | 22.2 C (72.0 F) | 3.9 C (7.0 F) | 20 years | 22 of 100 (Routine) |
| 13 July 2026 | Heart Butte Dam, US | daily high max (Tie) | 41.1 C (106.0 F) | tie | 23 years | 2 of 100 (Routine) |
| 24 June 2026 | Heart Butte Dam, US | daily low max (Tie) | 18.9 C (66.0 F) | tie | 8 years | 1 of 100 (Routine) |
| 29 May 2026 | Heart Butte Dam, US | daily high min | 17.8 C (64.0 F) | 1.1 C (2.0 F) | 12 years | 9 of 100 (Routine) |
| 28 May 2026 | Heart Butte Dam, US | daily high max (Tie) | 31.7 C (89.1 F) | tie | 28 years | 3 of 100 (Routine) |
| 18 May 2026 | Heart Butte Dam, US | daily low max | 6.1 C (43.0 F) | 2.8 C (5.0 F) | 7 years | 10 of 100 (Routine) |
| 12 May 2026 | Heart Butte Dam, US | daily low min | -6.1 C (21.0 F) | 1.7 C (3.1 F) | 12 years | 10 of 100 (Routine) |
| 17 March 2026 | Heart Butte Dam, US | daily low min | -21.7 C (-7.1 F) | 1.7 C (3.1 F) | 32 years | 15 of 100 (Routine) |
| 16 March 2026 | Heart Butte Dam, US | daily low max | -11.1 C (12.0 F) | 6.1 C (11.0 F) | 25 years | 17 of 100 (Routine) |
| 9 March 2026 | Heart Butte Dam, US | daily high max | 20.0 C (68.0 F) | 4.4 C (7.9 F) | 4 years | 10 of 100 (Routine) |
| 18 February 2026 | Heart Butte Dam, US | daily rain | 5.3 mm (0.21 in) | 1.5 mm (0.06 in) | 28 years | 17 of 100 (Routine) |
| 17 February 2026 | Heart Butte Dam, US | daily high min (Tie) | 0.0 C (32.0 F) | tie | 28 years | 3 of 100 (Routine) |
| 15 January 2026 | Heart Butte Dam, US | daily high max (Tie) | 7.2 C (45.0 F) | tie | 22 years | 2 of 100 (Routine) |
Climate Trend
39 complete years, 1985 to 2023| Year | Annual mean temperature | Difference from the station mean |
|---|---|---|
| 1985 | 4.5 C | -1.49 C |
| 1986 | 6.3 C | +0.31 C |
| 1987 | 7.9 C | +1.92 C |
| 1988 | 6.6 C | +0.65 C |
| 1989 | 5.4 C | -0.57 C |
| 1990 | 6.8 C | +0.87 C |
| 1991 | 6.8 C | +0.86 C |
| 1992 | 6.2 C | +0.25 C |
| 1993 | 4.3 C | -1.66 C |
| 1994 | 5.4 C | -0.60 C |
| 1995 | 5.4 C | -0.55 C |
| 1996 | 3.5 C | -2.43 C |
| 1997 | 6.0 C | +0.03 C |
| 1998 | 7.2 C | +1.25 C |
| 1999 | 7.2 C | +1.20 C |
| 2000 | 6.1 C | +0.11 C |
| 2001 | 6.7 C | +0.79 C |
| 2002 | 6.2 C | +0.23 C |
| 2003 | 6.0 C | +0.02 C |
| 2004 | 5.9 C | -0.06 C |
| 2005 | 6.8 C | +0.87 C |
| 2006 | 7.6 C | +1.63 C |
| 2007 | 6.7 C | +0.71 C |
| 2008 | 5.2 C | -0.80 C |
| 2009 | 4.2 C | -1.80 C |
| 2010 | 5.4 C | -0.60 C |
| 2011 | 5.3 C | -0.61 C |
| 2012 | 7.6 C | +1.64 C |
| 2013 | 5.0 C | -0.95 C |
| 2014 | 4.8 C | -1.17 C |
| 2015 | 7.3 C | +1.37 C |
| 2016 | 7.4 C | +1.49 C |
| 2017 | 6.3 C | +0.38 C |
| 2018 | 4.8 C | -1.11 C |
| 2019 | 3.5 C | -2.43 C |
| 2020 | 6.3 C | +0.37 C |
| 2021 | 6.9 C | +0.97 C |
| 2022 | 4.9 C | -1.09 C |
| 2023 | 5.8 C | -0.12 C |
The fitted trend in annual mean temperature here over 1985 to 2023 is -0.1 C (-0.4 to 0.2) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: -0.1 F (-0.7 to 0.4) per decade. The slope is a straight line fitted to 39 complete years; the brackets give its 95 percent interval.
| Measure | Per decade (C) | Per decade (F) | Period | Complete years | Reading |
|---|---|---|---|---|---|
| Annual mean temperature | -0.1 C (-0.4 to 0.2) per decade | -0.1 F (-0.7 to 0.4) per decade | 1985 to 2023 | 39 | Not clearly different from zero |
| Mean daily maximum | -0.1 C (-0.5 to 0.3) per decade | -0.2 F (-0.9 to 0.5) per decade | 1985 to 2023 | 39 | Not clearly different from zero |
| Mean daily minimum | -0.04 C (-0.33 to 0.24) per decade | -0.1 F (-0.6 to 0.4) per decade | 1985 to 2023 | 39 | Not clearly different from zero |
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
1984 to 2026| Measure | Record | Year of the record | Median year | Years with a value |
|---|---|---|---|---|
| Hottest day (TXx) | 43.9 C (111.0 F) | 2006 | 38.3 C (100.9 F) | 43 |
| Coldest night (TNn) | -41.1 C (-42.0 F) | 2025 | -33.9 C (-29.0 F) | 43 |
| Wettest day (Rx1day) | 114.8 mm (4.5 in) | 2001 | 36.8 mm (1.4 in) | 43 |
| Wettest five days (Rx5day) | 146.3 mm (5.8 in) | 2001 | 56.1 mm (2.2 in) | 43 |
| Longest dry spell (CDD) | 60 days | 1985 | 32 days | 43 |
Hottest day (TXx)
| Year | Hottest day (TXx) |
|---|---|
| 1984 | 33.9 C (93.0 F) |
| 1985 | 38.3 C (100.9 F) |
| 1986 | 37.2 C (99.0 F) |
| 1987 | 36.1 C (97.0 F) |
| 1988 | 40.6 C (105.1 F) |
| 1989 | 41.7 C (107.1 F) |
| 1990 | 36.1 C (97.0 F) |
| 1991 | 40.0 C (104.0 F) |
| 1992 | 35.0 C (95.0 F) |
| 1993 | 33.9 C (93.0 F) |
| 1994 | 37.2 C (99.0 F) |
| 1995 | 38.3 C (100.9 F) |
| 1996 | 38.3 C (100.9 F) |
| 1997 | 38.3 C (100.9 F) |
| 1998 | 36.7 C (98.1 F) |
| 1999 | 39.4 C (102.9 F) |
| 2000 | 40.6 C (105.1 F) |
| 2001 | 38.9 C (102.0 F) |
| 2002 | 43.3 C (109.9 F) |
| 2003 | 41.1 C (106.0 F) |
| 2004 | 38.3 C (100.9 F) |
| 2005 | 39.4 C (102.9 F) |
| 2006 | 43.9 C (111.0 F) |
| 2007 | 43.3 C (109.9 F) |
| 2008 | 38.3 C (100.9 F) |
| 2009 | 36.1 C (97.0 F) |
| 2010 | 38.9 C (102.0 F) |
| 2011 | 35.6 C (96.1 F) |
| 2012 | 40.6 C (105.1 F) |
| 2013 | 35.0 C (95.0 F) |
| 2014 | 35.6 C (96.1 F) |
| 2015 | 37.8 C (100.0 F) |
| 2016 | 37.8 C (100.0 F) |
| 2017 | 40.0 C (104.0 F) |
| 2018 | 38.9 C (102.0 F) |
| 2019 | 33.3 C (91.9 F) |
| 2020 | 36.1 C (97.0 F) |
| 2021 | 38.3 C (100.9 F) |
| 2022 | 37.2 C (99.0 F) |
| 2023 | 35.6 C (96.1 F) |
| 2024 | 40.6 C (105.1 F) |
| 2025 | 35.6 C (96.1 F) |
| 2026 | 41.1 C (106.0 F) |
Coldest night (TNn)
| Year | Coldest night (TNn) |
|---|---|
| 1984 | -31.7 C (-25.1 F) |
| 1985 | -33.9 C (-29.0 F) |
| 1986 | -33.9 C (-29.0 F) |
| 1987 | -23.3 C (-9.9 F) |
| 1988 | -38.3 C (-36.9 F) |
| 1989 | -38.3 C (-36.9 F) |
| 1990 | -37.8 C (-36.0 F) |
| 1991 | -28.9 C (-20.0 F) |
| 1992 | -31.1 C (-24.0 F) |
| 1993 | -33.3 C (-27.9 F) |
| 1994 | -39.4 C (-38.9 F) |
| 1995 | -31.1 C (-24.0 F) |
| 1996 | -37.8 C (-36.0 F) |
| 1997 | -31.1 C (-24.0 F) |
| 1998 | -35.0 C (-31.0 F) |
| 1999 | -33.9 C (-29.0 F) |
| 2000 | -31.7 C (-25.1 F) |
| 2001 | -30.6 C (-23.1 F) |
| 2002 | -28.9 C (-20.0 F) |
| 2003 | -30.6 C (-23.1 F) |
| 2004 | -32.2 C (-26.0 F) |
| 2005 | -36.1 C (-33.0 F) |
| 2006 | -28.9 C (-20.0 F) |
| 2007 | -35.6 C (-32.1 F) |
| 2008 | -31.1 C (-24.0 F) |
| 2009 | -38.9 C (-38.0 F) |
| 2010 | -36.7 C (-34.1 F) |
| 2011 | -35.0 C (-31.0 F) |
| 2012 | -27.2 C (-17.0 F) |
| 2013 | -37.2 C (-35.0 F) |
| 2014 | -29.4 C (-20.9 F) |
| 2015 | -29.4 C (-20.9 F) |
| 2016 | -32.8 C (-27.0 F) |
| 2017 | -35.0 C (-31.0 F) |
| 2018 | -36.1 C (-33.0 F) |
| 2019 | -35.0 C (-31.0 F) |
| 2020 | -29.4 C (-20.9 F) |
| 2021 | -37.2 C (-35.0 F) |
| 2022 | -31.7 C (-25.1 F) |
| 2023 | -33.9 C (-29.0 F) |
| 2024 | -35.6 C (-32.1 F) |
| 2025 | -41.1 C (-42.0 F) |
| 2026 | -28.9 C (-20.0 F) |
Wettest day (Rx1day)
| Year | Wettest day (Rx1day) |
|---|---|
| 1984 | 9.7 mm (0.38 in) |
| 1985 | 56.6 mm (2.2 in) |
| 1986 | 62.2 mm (2.4 in) |
| 1987 | 35.6 mm (1.4 in) |
| 1988 | 36.8 mm (1.4 in) |
| 1989 | 37.6 mm (1.5 in) |
| 1990 | 37.8 mm (1.5 in) |
| 1991 | 47.5 mm (1.9 in) |
| 1992 | 38.1 mm (1.5 in) |
| 1993 | 61.5 mm (2.4 in) |
| 1994 | 46.7 mm (1.8 in) |
| 1995 | 32.0 mm (1.3 in) |
| 1996 | 28.4 mm (1.1 in) |
| 1997 | 62.7 mm (2.5 in) |
| 1998 | 54.9 mm (2.2 in) |
| 1999 | 61.0 mm (2.4 in) |
| 2000 | 36.1 mm (1.4 in) |
| 2001 | 114.8 mm (4.5 in) |
| 2002 | 29.5 mm (1.2 in) |
| 2003 | 34.3 mm (1.4 in) |
| 2004 | 30.5 mm (1.2 in) |
| 2005 | 27.7 mm (1.1 in) |
| 2006 | 20.3 mm (0.8 in) |
| 2007 | 54.1 mm (2.1 in) |
| 2008 | 23.9 mm (0.9 in) |
| 2009 | 32.5 mm (1.3 in) |
| 2010 | 30.5 mm (1.2 in) |
| 2011 | 77.5 mm (3.1 in) |
| 2012 | 55.9 mm (2.2 in) |
| 2013 | 53.6 mm (2.1 in) |
| 2014 | 56.1 mm (2.2 in) |
| 2015 | 30.7 mm (1.2 in) |
| 2016 | 39.9 mm (1.6 in) |
| 2017 | 25.9 mm (1.0 in) |
| 2018 | 26.4 mm (1.0 in) |
| 2019 | 43.7 mm (1.7 in) |
| 2020 | 30.5 mm (1.2 in) |
| 2021 | 26.2 mm (1.0 in) |
| 2022 | 40.9 mm (1.6 in) |
| 2023 | 26.4 mm (1.0 in) |
| 2024 | 25.9 mm (1.0 in) |
| 2025 | 70.1 mm (2.8 in) |
| 2026 | 24.1 mm (0.9 in) |
Wettest five days (Rx5day)
| Year | Wettest five days (Rx5day) |
|---|---|
| 1984 | 13.3 mm (0.5 in) |
| 1985 | 66.5 mm (2.6 in) |
| 1986 | 72.9 mm (2.9 in) |
| 1987 | 61.0 mm (2.4 in) |
| 1988 | 48.4 mm (1.9 in) |
| 1989 | 62.4 mm (2.5 in) |
| 1990 | 52.2 mm (2.1 in) |
| 1991 | 49.0 mm (1.9 in) |
| 1992 | 77.8 mm (3.1 in) |
| 1993 | 111.8 mm (4.4 in) |
| 1994 | 64.9 mm (2.6 in) |
| 1995 | 54.7 mm (2.2 in) |
| 1996 | 56.9 mm (2.2 in) |
| 1997 | 62.7 mm (2.5 in) |
| 1998 | 99.6 mm (3.9 in) |
| 1999 | 71.5 mm (2.8 in) |
| 2000 | 72.9 mm (2.9 in) |
| 2001 | 146.3 mm (5.8 in) |
| 2002 | 59.0 mm (2.3 in) |
| 2003 | 44.9 mm (1.8 in) |
| 2004 | 36.9 mm (1.5 in) |
| 2005 | 41.9 mm (1.6 in) |
| 2006 | 34.3 mm (1.4 in) |
| 2007 | 56.1 mm (2.2 in) |
| 2008 | 39.6 mm (1.6 in) |
| 2009 | 44.7 mm (1.8 in) |
| 2010 | 53.3 mm (2.1 in) |
| 2011 | 87.4 mm (3.4 in) |
| 2012 | 58.4 mm (2.3 in) |
| 2013 | 77.8 mm (3.1 in) |
| 2014 | 80.7 mm (3.2 in) |
| 2015 | 39.4 mm (1.6 in) |
| 2016 | 42.7 mm (1.7 in) |
| 2017 | 59.7 mm (2.4 in) |
| 2018 | 52.0 mm (2.0 in) |
| 2019 | 74.0 mm (2.9 in) |
| 2020 | 47.5 mm (1.9 in) |
| 2021 | 44.8 mm (1.8 in) |
| 2022 | 56.7 mm (2.2 in) |
| 2023 | 49.1 mm (1.9 in) |
| 2024 | 31.2 mm (1.2 in) |
| 2025 | 6.1 mm (0.24 in) |
| 2026 | 42.3 mm (1.7 in) |
Longest dry spell (CDD)
| Year | Longest dry spell (CDD) |
|---|---|
| 1984 | 28 days |
| 1985 | 60 days |
| 1986 | 24 days |
| 1987 | 45 days |
| 1988 | 44 days |
| 1989 | 39 days |
| 1990 | 45 days |
| 1991 | 38 days |
| 1992 | 38 days |
| 1993 | 26 days |
| 1994 | 25 days |
| 1995 | 37 days |
| 1996 | 28 days |
| 1997 | 40 days |
| 1998 | 23 days |
| 1999 | 39 days |
| 2000 | 21 days |
| 2001 | 37 days |
| 2002 | 19 days |
| 2003 | 38 days |
| 2004 | 30 days |
| 2005 | 36 days |
| 2006 | 57 days |
| 2007 | 23 days |
| 2008 | 32 days |
| 2009 | 44 days |
| 2010 | 32 days |
| 2011 | 35 days |
| 2012 | 31 days |
| 2013 | 39 days |
| 2014 | 28 days |
| 2015 | 21 days |
| 2016 | 26 days |
| 2017 | 36 days |
| 2018 | 24 days |
| 2019 | 19 days |
| 2020 | 41 days |
| 2021 | 35 days |
| 2022 | 51 days |
| 2023 | 31 days |
| 2024 | 31 days |
| 2025 | 9 days |
| 2026 | 12 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
39 years with a frostAcross 39 years with a frost, the median last spring frost at Heart Butte Dam falls on 15 May and the median first autumn frost on 30 September, which leaves a median of 137 days between them.
Fitted over all years, the growing season changes by +1.5 days per decade at this station.
| Measure | Median, all years | Earliest period | Recent period (1994 to 2023) | Recent against earliest | Fitted trend |
|---|---|---|---|---|---|
| Last spring frost | 15 May | n/a | 15 May | n/a | +1.2 days per decade |
| First autumn frost | 30 September | n/a | 2 October | n/a | +2.7 days per decade |
| Growing days | 137 days | n/a | 138 days | n/a | +1.5 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
34 years, 1985 to 2021A day with at least 39.2 mm (1.5 in) of rain is expected about once in 2 years. A day with at least 114.7 mm (4.5 in) of rain is expected about once in 100 years.
| Expected about once in | A day with at least | Note |
|---|---|---|
| 2 years | 39.2 mm (1.5 in) | |
| 5 years | 54.9 mm (2.2 in) | |
| 10 years | 66.8 mm (2.6 in) | |
| 25 years | 84.1 mm (3.3 in) | |
| 50 years | 98.6 mm (3.9 in) | Longer than the 34 years of record |
| 100 years | 114.7 mm (4.5 in) | Longer than the 34 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, 34 years of values from 1985 to 2021.
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: 114.8 mm (4.5 in) in 2001; 77.5 mm (3.1 in) in 2011; 62.7 mm (2.5 in) in 1997.
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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 2026-10-14 (14 October 2026). Records are computed by this site and are not official.
Data as of . Last revised (2026-10-14).