Alton Threshold Days by Year (USC00420086)
16 fixed thresholds counted per year at Alton (USC00420086): hot days, frost, tropical nights and heavy rain, with the most days in a year.
Key Facts for Alton Thresholds
- Alton: nights with a minimum temperature at or below 0 C (32 F) in 109 years, most in 1970 with 224.
- Alton: nights with a minimum temperature at or below -10 C (14 F) in 109 years, most in 1964 with 80.
- Alton: days with a maximum temperature at or below 0 C (32 F) in 107 years, most in 1932 with 56.
- Alton: days with a maximum temperature at or above 30 C (86 F) in 104 years, most in 2024 with 67.
- 16 fixed thresholds have at least one qualifying day at Alton.
Days at or above 30 C (86 F)
104 years with a qualifying day| Year | Days | Decade average |
|---|---|---|
| 1917 | 17 | 10 |
| 1918 | 6 | 10 |
| 1919 | 7 | 10 |
| 1920 | 2 | 3 |
| 1921 | 1 | 3 |
| 1922 | 6 | 3 |
| 1923 | 3 | 3 |
| 1924 | 3 | 3 |
| 1925 | 3 | 3 |
| 1926 | 3 | 3 |
| 1927 | 3 | 3 |
| 1928 | 1 | 3 |
| 1929 | 5 | 3 |
| 1930 | 1 | 6 |
| 1931 | 9 | 6 |
| 1932 | 2 | 6 |
| 1933 | 7 | 6 |
| 1934 | 11 | 6 |
| 1936 | 5 | 6 |
| 1937 | 5 | 6 |
| 1938 | 2 | 6 |
| 1939 | 12 | 6 |
| 1940 | 17 | 8.7 |
| 1941 | 7 | 8.7 |
| 1942 | 22 | 8.7 |
| 1943 | 7 | 8.7 |
| 1944 | 2 | 8.7 |
| 1946 | 1 | 8.7 |
| 1947 | 6 | 8.7 |
| 1948 | 10 | 8.7 |
| 1949 | 6 | 8.7 |
| 1950 | 18 | 18.9 |
| 1951 | 19 | 18.9 |
| 1952 | 5 | 18.9 |
| 1953 | 11 | 18.9 |
| 1954 | 21 | 18.9 |
| 1955 | 22 | 18.9 |
| 1956 | 22 | 18.9 |
| 1957 | 18 | 18.9 |
| 1958 | 20 | 18.9 |
| 1959 | 33 | 18.9 |
| 1960 | 51 | 25.6 |
| 1961 | 42 | 25.6 |
| 1962 | 32 | 25.6 |
| 1963 | 25 | 25.6 |
| 1964 | 22 | 25.6 |
| 1965 | 8 | 25.6 |
| 1966 | 27 | 25.6 |
| 1967 | 18 | 25.6 |
| 1968 | 14 | 25.6 |
| 1969 | 17 | 25.6 |
| 1970 | 29 | 25.8 |
| 1971 | 26 | 25.8 |
| 1972 | 38 | 25.8 |
| 1973 | 21 | 25.8 |
| 1974 | 30 | 25.8 |
| 1975 | 12 | 25.8 |
| 1976 | 19 | 25.8 |
| 1977 | 23 | 25.8 |
| 1978 | 29 | 25.8 |
| 1979 | 31 | 25.8 |
| 1980 | 21 | 17.8 |
| 1981 | 34 | 17.8 |
| 1982 | 11 | 17.8 |
| 1983 | 6 | 17.8 |
| 1985 | 34 | 17.8 |
| 1986 | 16 | 17.8 |
| 1987 | 1 | 17.8 |
| 1988 | 15 | 17.8 |
| 1989 | 22 | 17.8 |
| 1990 | 24 | 20.1 |
| 1991 | 17 | 20.1 |
| 1992 | 13 | 20.1 |
| 1995 | 27 | 20.1 |
| 1996 | 39 | 20.1 |
| 1997 | 9 | 20.1 |
| 1998 | 24 | 20.1 |
| 1999 | 8 | 20.1 |
| 2000 | 43 | 39.2 |
| 2001 | 25 | 39.2 |
| 2002 | 59 | 39.2 |
| 2003 | 48 | 39.2 |
| 2004 | 30 | 39.2 |
| 2005 | 23 | 39.2 |
| 2006 | 31 | 39.2 |
| 2007 | 55 | 39.2 |
| 2009 | 39 | 39.2 |
| 2010 | 36 | 38 |
| 2011 | 37 | 38 |
| 2012 | 36 | 38 |
| 2013 | 34 | 38 |
| 2014 | 22 | 38 |
| 2015 | 29 | 38 |
| 2016 | 44 | 38 |
| 2017 | 44 | 38 |
| 2018 | 55 | 38 |
| 2019 | 43 | 38 |
| 2020 | 60 | 50.4 |
| 2021 | 52 | 50.4 |
| 2022 | 39 | 50.4 |
| 2023 | 30 | 50.4 |
| 2024 | 67 | 50.4 |
| 2025 | 59 | 50.4 |
| 2026 | 46 | 50.4 |
| Year | First date | Last date |
|---|---|---|
| 1917 | 1917-07-02 | 1917-08-24 |
| 1918 | 1918-06-09 | 1918-08-03 |
| 1919 | 1919-06-23 | 1919-09-12 |
| 1920 | 1920-06-20 | 1920-07-19 |
| 1921 | 1921-06-11 | 1921-06-11 |
| 1922 | 1922-07-04 | 1922-07-21 |
| 1923 | 1923-06-30 | 1923-07-03 |
| 1924 | 1924-06-29 | 1924-09-07 |
| 1925 | 1925-07-14 | 1925-07-17 |
| 1926 | 1926-06-26 | 1926-07-15 |
| 1927 | 1927-06-18 | 1927-07-18 |
| 1928 | 1928-07-27 | 1928-07-27 |
| 1929 | 1929-06-24 | 1929-07-02 |
| 1930 | 1930-06-12 | 1930-06-12 |
| 1931 | 1931-07-12 | 1931-08-24 |
| 1932 | 1932-07-06 | 1932-07-07 |
| 1933 | 1933-06-13 | 1933-08-14 |
| 1934 | 1934-06-30 | 1934-08-02 |
| 1936 | 1936-06-14 | 1936-06-21 |
| 1937 | 1937-06-19 | 1937-08-11 |
| 1938 | 1938-08-01 | 1938-08-04 |
| 1939 | 1939-07-08 | 1939-08-17 |
| 1940 | 1940-06-13 | 1940-08-22 |
| 1941 | 1941-07-06 | 1941-07-31 |
| 1942 | 1942-07-04 | 1942-08-17 |
| 1943 | 1943-07-09 | 1943-08-27 |
| 1944 | 1944-07-17 | 1944-08-13 |
| 1946 | 1946-07-10 | 1946-07-10 |
| 1947 | 1947-07-18 | 1947-07-29 |
| 1948 | 1948-07-14 | 1948-09-03 |
| 1949 | 1949-07-15 | 1949-08-31 |
| 1950 | 1950-06-28 | 1950-09-03 |
| 1951 | 1951-06-27 | 1951-08-18 |
| 1952 | 1952-07-23 | 1952-08-05 |
| 1953 | 1953-06-22 | 1953-08-08 |
| 1954 | 1954-06-21 | 1954-08-31 |
| 1955 | 1955-06-07 | 1955-09-07 |
| 1956 | 1956-06-11 | 1956-09-17 |
| 1957 | 1957-06-23 | 1957-09-08 |
| 1958 | 1958-07-09 | 1958-08-31 |
| 1959 | 1959-06-17 | 1959-09-09 |
| 1960 | 1960-06-03 | 1960-08-30 |
| 1961 | 1961-06-17 | 1961-08-22 |
| 1962 | 1962-06-20 | 1962-09-18 |
| 1963 | 1963-07-01 | 1963-08-16 |
| 1964 | 1964-06-25 | 1964-08-11 |
| 1965 | 1965-07-05 | 1965-08-13 |
| 1966 | 1966-06-14 | 1966-08-18 |
| 1967 | 1967-07-01 | 1967-08-24 |
| 1968 | 1968-06-17 | 1968-07-26 |
| 1969 | 1969-07-01 | 1969-08-26 |
| 1970 | 1970-06-20 | 1970-08-30 |
| 1971 | 1971-06-16 | 1971-09-13 |
| 1972 | 1972-06-28 | 1972-08-22 |
| 1973 | 1973-06-07 | 1973-08-13 |
| 1974 | 1974-06-11 | 1974-08-29 |
| 1975 | 1975-07-06 | 1975-08-13 |
| 1976 | 1976-06-27 | 1976-08-30 |
| 1977 | 1977-06-23 | 1977-09-07 |
| 1978 | 1978-06-08 | 1978-09-03 |
| 1979 | 1979-06-13 | 1979-09-08 |
| 1980 | 1980-06-26 | 1980-08-13 |
| 1981 | 1981-06-19 | 1981-09-20 |
| 1982 | 1982-06-27 | 1982-08-01 |
| 1983 | 1983-05-29 | 1983-09-15 |
| 1985 | 1985-06-07 | 1985-08-31 |
| 1986 | 1986-05-30 | 1986-09-05 |
| 1987 | 1987-07-14 | 1987-07-14 |
| 1988 | 1988-06-21 | 1988-08-19 |
| 1989 | 1989-06-15 | 1989-08-07 |
| 1990 | 1990-06-21 | 1990-09-15 |
| 1991 | 1991-07-02 | 1991-08-21 |
| 1992 | 1992-07-05 | 1992-08-20 |
| 1995 | 1995-07-07 | 1995-09-04 |
| 1996 | 1996-05-12 | 1996-09-01 |
| 1997 | 1997-07-05 | 1997-08-08 |
| 1998 | 1998-06-28 | 1998-08-30 |
| 1999 | 1999-06-29 | 1999-07-25 |
| 2000 | 2000-05-22 | 2000-09-17 |
| 2001 | 2001-06-07 | 2001-08-28 |
| 2002 | 2002-05-29 | 2002-09-04 |
| 2003 | 2003-05-27 | 2003-09-28 |
| 2004 | 2004-06-03 | 2004-09-01 |
| 2005 | 2005-06-20 | 2005-08-29 |
| 2006 | 2006-06-04 | 2006-08-24 |
| 2007 | 2007-06-14 | 2007-09-09 |
| 2009 | 2009-06-24 | 2009-09-02 |
| 2010 | 2010-06-05 | 2010-09-28 |
| 2011 | 2011-06-22 | 2011-09-03 |
| 2012 | 2012-06-01 | 2012-09-09 |
| 2013 | 2013-06-07 | 2013-08-21 |
| 2014 | 2014-06-06 | 2014-07-26 |
| 2015 | 2015-06-18 | 2015-09-12 |
| 2016 | 2016-06-04 | 2016-08-14 |
| 2017 | 2017-06-16 | 2017-09-06 |
| 2018 | 2018-06-04 | 2018-09-09 |
| 2019 | 2019-07-09 | 2019-09-07 |
| 2020 | 2020-05-28 | 2020-09-24 |
| 2021 | 2021-06-02 | 2021-09-09 |
| 2022 | 2022-06-08 | 2022-09-08 |
| 2023 | 2023-07-01 | 2023-08-29 |
| 2024 | 2024-05-31 | 2024-09-30 |
| 2025 | 2025-05-31 | 2025-09-02 |
| 2026 | 2026-06-13 | 2026-08-26 |
Every Fixed Threshold
| Threshold | Years with a qualifying day | Most days in a year | Year | Latest year days |
|---|---|---|---|---|
| 30 C (86 F): Days | 104 | 67 | 2024 | 46 |
| 35 C (95 F): Days | 29 | 8 | 2021 | 2 |
| 90 F (32.2 C): Days | 75 | 34 | 2024 | 19 |
| 100 F (37.8 C): Days | 1 | 1 | 2021 | 1 |
| 0 C (32 F): Ice days (max | 107 | 56 | 1932 | 4 |
| 0 C (32 F): Frost days (min | 109 | 224 | 1970 | 93 |
| -10 C (14 F): Days with min | 109 | 80 | 1964 | 8 |
| -20 C (-4 F): Days with min | 64 | 14 | 1937 | 2 |
| -30 C (-22 F): Days with min | 1 | 1 | 1990 | 1 |
| 20 C (68 F): Tropical nights (min | 8 | 3 | 1928 | 1 |
| 10 mm (0.39 in): Days with 10 mm or more rain | 99 | 25 | 2019 | 12 |
| 25 mm (0.98 in): Days with 25 mm or more rain | 88 | 8 | 2005 | 3 |
| 50 mm (1.97 in): Days with 50 mm or more rain | 14 | 4 | 2010 | 1 |
| 10 cm (3.9 in): Days with 10 cm or more snowfall | 94 | 18 | 1979 | 3 |
| 25 cm (9.8 in): Days with 25 cm or more snowfall | 63 | 7 | 1949 | 2 |
| 50 cm (19.7 in): Days with 50 cm or more snowfall | 5 | 1 | 1936 | 1 |
Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1917.
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 2026-10-17 (17 October 2026). Threshold counts are computed by this site.
Data as of . Last revised (2026-10-17).