Alton 1 W Threshold Days by Year

21 fixed thresholds counted per year at Alton 1 W (USC00140201): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Alton 1 W Thresholds

Alton 1 W: days with a maximum temperature at or above 30 C (86 F) in 95 years, most in 1939 with 131.
Alton 1 W: days with a maximum temperature at or above 35 C (95 F) in 95 years, most in 1936 with 86.
Alton 1 W: days with a maximum temperature at or above 90 F (32.2 C) in 95 years, most in 1936 with 102.
Alton 1 W: days with a maximum temperature at or below 0 C (32 F) in 95 years, most in 1960 with 46.
21 fixed thresholds have at least one qualifying day at Alton 1 W.

Days at or above 30 C (86 F)

95 years with a qualifying day

Days per year at Alton 1 W with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 131 in 1939.

Days at or above 30 C (86 F) per year at Alton 1 W
Year	Days	Decade average
1903	67	83
1904	62	83
1905	89	83
1906	100	83
1909	97	83
1910	99	90.7
1911	101	90.7
1912	82	90.7
1913	115	90.7
1914	112	90.7
1915	32	90.7
1916	90	90.7
1917	84	90.7
1918	99	90.7
1919	93	90.7
1920	83	94.9
1921	122	94.9
1922	108	94.9
1923	84	94.9
1924	84	94.9
1925	110	94.9
1926	107	94.9
1927	97	94.9
1928	75	94.9
1929	79	94.9
1930	83	104.3
1931	113	104.3
1932	95	104.3
1933	114	104.3
1934	113	104.3
1935	75	104.3
1936	116	104.3
1938	99	104.3
1939	131	104.3
1940	100	86
1941	77	86
1942	83	86
1943	100	86
1944	77	86
1945	80	86
1946	86	86
1947	98	86
1948	96	86
1949	63	86
1950	55	86.2
1951	57	86.2
1952	96	86.2
1953	103	86.2
1954	107	86.2
1955	104	86.2
1956	122	86.2
1957	56	86.2
1958	69	86.2
1959	93	86.2
1960	77	88
1961	67	88
1962	81	88
1963	113	88
1964	101	88
1965	89	88
1966	102	88
1967	72	88
1968	99	88
1969	79	88
1970	105	92.5
1971	99	92.5
1973	80	92.5
1974	84	92.5
1975	92	92.5
1976	98	92.5
1977	87	92.5
1978	95	92.5
1980	110	93.9
1982	69	93.9
1985	88	93.9
1986	95	93.9
1987	98	93.9
1988	112	93.9
1989	85	93.9
1990	90	84.4
1991	111	84.4
1992	59	84.4
1993	63	84.4
1994	99	84.4
1995	81	84.4
1996	80	84.4
1997	87	84.4
1998	95	84.4
1999	79	84.4
2000	106	93.8
2001	104	93.8
2003	86	93.8
2004	79	93.8
2005	87	93.8
2006	101	93.8

For each year, a bar from the first to the last day at Alton 1 W meeting 30 C (86 F).

First to last qualifying date each year at Alton 1 W
Year	First date	Last date
1903	1903-05-20	1903-10-19
1904	1904-03-02	1904-10-09
1905	1905-04-09	1905-10-12
1906	1906-04-11	1906-10-12
1909	1909-04-17	1909-10-06
1910	1910-03-21	1910-10-17
1911	1911-04-28	1911-10-05
1912	1912-04-05	1912-10-28
1913	1913-04-01	1913-10-14
1914	1914-04-16	1914-10-06
1915	1915-04-27	1915-10-30
1916	1916-03-12	1916-10-07
1917	1917-03-30	1917-09-23
1918	1918-05-06	1918-10-16
1919	1919-06-07	1919-10-02
1920	1920-05-22	1920-10-10
1921	1921-03-04	1921-10-24
1922	1922-05-05	1922-10-28
1923	1923-05-31	1923-09-28
1924	1924-04-15	1924-10-18
1925	1925-03-23	1925-09-29
1926	1926-04-16	1926-10-17
1927	1927-04-26	1927-10-28
1928	1928-04-02	1928-10-11
1929	1929-04-03	1929-09-25
1930	1930-04-09	1930-10-10
1931	1931-04-07	1931-10-10
1932	1932-04-01	1932-10-02
1933	1933-05-17	1933-10-05
1934	1934-04-10	1934-10-26
1935	1935-03-14	1935-09-23
1936	1936-04-12	1936-10-19
1938	1938-06-05	1938-10-31
1939	1939-04-22	1939-10-23
1940	1940-04-01	1940-10-25
1941	1941-05-14	1941-09-20
1942	1942-04-04	1942-10-08
1943	1943-03-29	1943-10-19
1944	1944-05-12	1944-09-22
1945	1945-04-09	1945-11-05
1946	1946-03-31	1946-09-26
1947	1947-05-14	1947-10-21
1948	1948-04-10	1948-10-15
1949	1949-04-25	1949-10-08
1950	1950-04-22	1950-10-31
1951	1951-04-24	1951-10-03
1952	1952-05-04	1952-10-24
1953	1953-04-21	1953-10-10
1954	1954-04-06	1954-10-03
1955	1955-04-19	1955-10-12
1956	1956-04-01	1956-10-17
1957	1957-06-05	1957-10-06
1958	1958-05-26	1958-10-19
1959	1959-04-04	1959-10-25
1960	1960-04-21	1960-10-05
1961	1961-04-19	1961-10-17
1962	1962-04-20	1962-10-14
1963	1963-03-24	1963-10-15
1964	1964-04-15	1964-10-07
1965	1965-04-20	1965-10-10
1966	1966-05-04	1966-10-13
1967	1967-03-23	1967-10-13
1968	1968-03-28	1968-10-15
1969	1969-05-26	1969-10-03
1970	1970-04-27	1970-10-06
1971	1971-03-31	1971-10-10
1973	1973-05-18	1973-10-09
1974	1974-05-10	1974-10-11
1975	1975-05-17	1975-10-22
1976	1976-03-25	1976-10-14
1977	1977-04-27	1977-10-21
1978	1978-03-31	1978-10-21
1980	1980-04-20	1980-11-06
1982	1982-06-06	1982-10-06
1985	1985-04-15	1985-10-08
1986	1986-02-26	1986-09-29
1987	1987-04-18	1987-10-05
1988	1988-03-22	1988-10-14
1989	1989-03-27	1989-10-26
1990	1990-04-23	1990-10-27
1991	1991-03-27	1991-10-23
1992	1992-04-15	1992-10-22
1993	1993-05-08	1993-10-07
1994	1994-03-18	1994-10-01
1995	1995-03-22	1995-10-17
1996	1996-04-03	1996-10-15
1997	1997-03-21	1997-10-07
1998	1998-05-14	1998-09-29
1999	1999-05-31	1999-11-14
2000	2000-04-06	2000-10-19
2001	2001-04-20	2001-10-10
2003	2003-04-02	2003-10-23
2004	2004-04-17	2004-10-29
2005	2005-05-11	2005-10-19
2006	2006-04-14	2006-11-09

Every Fixed Threshold

Fixed thresholds at Alton 1 W
Threshold	Years with a qualifying day	Most days in a year	Year	Latest year days
30 C (86 F): Days	95	131	1939	101
35 C (95 F): Days	95	86	1936	46
40 C (104 F): Days	77	44	1936	8
45 C (113 F): Days	7	9	1936	1
90 F (32.2 C): Days	95	102	1936	75
100 F (37.8 C): Days	90	62	1936	21
110 F (43.3 C): Days	30	21	1936	1
120 F (48.9 C): Days	1	1	1936	1
0 C (32 F): Ice days (max	95	46	1960	10
0 C (32 F): Frost days (min	94	170	1997	154
-10 C (14 F): Days with min	94	71	1989	22
-20 C (-4 F): Days with min	90	16	1905	5
-30 C (-22 F): Days with min	9	4	1989	4
20 C (68 F): Tropical nights (min	94	69	1936	25
25 C (77 F): Days with min	58	29	1934	2
10 mm (0.39 in): Days with 10 mm or more rain	95	37	1993	21
25 mm (0.98 in): Days with 25 mm or more rain	95	14	1973	3
50 mm (1.97 in): Days with 50 mm or more rain	59	8	1973	1
100 mm (3.94 in): Days with 100 mm or more rain	6	2	1912	2
10 cm (3.9 in): Days with 10 cm or more snowfall	53	6	1997	1
25 cm (9.8 in): Days with 25 cm or more snowfall	8	1	1924	1

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1903.

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Data for Alton 1 W threshold days by year: CSV or JSON. Field meanings are on the data page.

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 2025-12-31. Last revised 31 December 2025 (2025-12-31).

Alton 1 W Threshold Days by Year

Key Facts for Alton 1 W Thresholds

Days at or above 30 C (86 F)

Every Fixed Threshold

Download the Data

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