Daily records
Page built 2026-10-19
Data as of 2026-10-17
Search
Built 2026-10-19 (19 October 2026)

Alton Threshold Days by Year (USC00230127)

18 fixed thresholds counted per year at Alton (USC00230127): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Alton Thresholds

  • Alton: days with 10 mm (0.39 in) or more of precipitation in 52 years, most in 1951 with 55.
  • Alton: days with 25 mm (0.98 in) or more of precipitation in 52 years, most in 2011 with 25.
  • Alton: days with 50 mm (1.97 in) or more of precipitation in 52 years, most in 2011 with 10.
  • Alton: days with a maximum temperature at or above 30 C (86 F) in 30 years, most in 1998 with 101.
  • 18 fixed thresholds have at least one qualifying day at Alton.
30 years with a qualifying day
Days at or above 30 C (86 F) per year at Alton Days per year at Alton with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 101 in 1998. 0501001501963: 911964: 831969: 821970: 731971: 801972: 791973: 721974: 581975: 801976: 671977: 901978: 941995: 771996: 741997: 721998: 1011999: 912000: 852001: 842002: 832003: 562004: 492005: 962006: 902007: 952008: 602011: 932024: 812025: 802026: 951963197019731976199519982001200420072024
Days per year at Alton with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 101 in 1998.
Days at or above 30 C (86 F) per year at Alton
YearDaysDecade average
19639185.3
19648385.3
19698285.3
19707377
19718077
19727977
19737277
19745877
19758077
19766777
19779077
19789477
19957783
19967483
19977283
199810183
19999183
20008577.6
20018477.6
20028377.6
20035677.6
20044977.6
20059677.6
20069077.6
20079577.6
20086077.6
20119393
20248185.3
20258085.3
20269585.3
First to last qualifying date each year at Alton For each year, a bar from the first to the last day at Alton meeting 30 C (86 F). 1963: 1 April 1963 to 22 October 19631964: 17 May 1964 to 21 October 19641969: 5 May 1969 to 3 October 19691970: 28 April 1970 to 20 September 19701971: 2 June 1971 to 2 October 19711972: 13 April 1972 to 21 September 19721973: 10 May 1973 to 8 October 19731974: 19 May 1974 to 26 August 19741975: 18 May 1975 to 13 October 19751976: 10 June 1976 to 12 October 19761977: 14 May 1977 to 1 October 19771978: 8 April 1978 to 21 October 19781995: 10 April 1995 to 15 September 19951996: 18 May 1996 to 12 September 19961997: 22 March 1997 to 8 October 19971998: 13 May 1998 to 1 October 19981999: 3 June 1999 to 17 October 19992000: 20 April 2000 to 6 October 20002001: 10 April 2001 to 14 September 20012002: 18 April 2002 to 5 October 20022003: 11 June 2003 to 21 October 20032004: 21 May 2004 to 24 September 20042005: 12 May 2005 to 20 October 20052006: 14 April 2006 to 17 September 20062007: 1 May 2007 to 9 October 20072008: 20 May 2008 to 13 September 20082011: 10 April 2011 to 17 October 20112024: 28 February 2024 to 13 October 20242025: 17 May 2025 to 3 October 20252026: 21 March 2026 to 2 October 202619631971197519951999200320072025JanFebMarAprMayJunJulAugSepOctNovDec
For each year, a bar from the first to the last day at Alton meeting 30 C (86 F).
First to last qualifying date each year at Alton
YearFirst dateLast date
19631963-04-011963-10-22
19641964-05-171964-10-21
19691969-05-051969-10-03
19701970-04-281970-09-20
19711971-06-021971-10-02
19721972-04-131972-09-21
19731973-05-101973-10-08
19741974-05-191974-08-26
19751975-05-181975-10-13
19761976-06-101976-10-12
19771977-05-141977-10-01
19781978-04-081978-10-21
19951995-04-101995-09-15
19961996-05-181996-09-12
19971997-03-221997-10-08
19981998-05-131998-10-01
19991999-06-031999-10-17
20002000-04-202000-10-06
20012001-04-102001-09-14
20022002-04-182002-10-05
20032003-06-112003-10-21
20042004-05-212004-09-24
20052005-05-122005-10-20
20062006-04-142006-09-17
20072007-05-012007-10-09
20082008-05-202008-09-13
20112011-04-102011-10-17
20242024-02-282024-10-13
20252025-05-172025-10-03
20262026-03-212026-10-02

Every Fixed Threshold

Fixed thresholds at Alton
ThresholdYears with a qualifying dayMost days in a yearYearLatest year days
30 C (86 F): Days30101199895
35 C (95 F): Days3041199928
40 C (104 F): Days4320001
90 F (32.2 C): Days3071199864
100 F (37.8 C): Days181220078
0 C (32 F): Ice days (max302419788
0 C (32 F): Frost days (min29125200859
-10 C (14 F): Days with min2935196314
-20 C (-4 F): Days with min7619772
20 C (68 F): Tropical nights (min2949199855
25 C (77 F): Days with min5119701
10 mm (0.39 in): Days with 10 mm or more rain5255195118
25 mm (0.98 in): Days with 25 mm or more rain522520114
50 mm (1.97 in): Days with 50 mm or more rain521020111
100 mm (3.94 in): Days with 100 mm or more rain10219581
200 mm (7.87 in): Days with 200 mm or more rain10n/a1
10 cm (3.9 in): Days with 10 cm or more snowfall25419601
25 cm (9.8 in): Days with 25 cm or more snowfall4219751

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1963.

Download the Data

  • Data for Alton 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 . Last revised (2026-10-17).