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Built 2026-10-14 (14 October 2026)

Alton Weather Records (USC00230127)

Record envelope, standing records and threshold days for Alton (USC00230127), Missouri, United States, with 87 years of record.

Key Facts for Alton

  • Alton (USC00230127) is a weather station in Missouri, United States at 36.69 latitude and -91.40 longitude, 248 m (812 ft) above sea level.
  • The station reports from 1940 to 2026, 87 years of record.
  • 1,464 records set at Alton still stand.
  • Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
  • Alton set a daily record precipitation of 38.9 mm (1.5 in) on 2 October 2026 (provisional).

Provisional Records

Records set in the last 60 days are provisional until they clear the revision window.

About the Station

  • Location: Missouri, United States, 36.69 latitude, -91.40 longitude.
  • Elevation: 248 m (812 ft).
  • Period of record: 1940 to 2026, 87 years.
  • Eligible elements: tmax, tmin, prcp, snow, snwd.

Daily Record Envelope and 2026

24 days at or beyond a record
Daily record high and record low at Alton, with 2026 drawn through them The band shows the record high and record low for each calendar day at Alton. The lines show the 2026 daily maximum and minimum. 24 days in 2026 matched or passed a record. Temperatures are in degrees Celsius. -40-200204060 JanFebMarAprMayJunJulAugSepOctNovDec
The band shows the record high and record low for each calendar day at Alton. The lines show the 2026 daily maximum and minimum. 24 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.
Daily record high and record low at Alton, with 2026 drawn through them
MonthHighest record highLowest record low2026 highest maximum2026 lowest minimum
Jan24.4 C (75.9 F)-27.8 C (-18.0 F)22.2 C (72.0 F)-18.9 C (-2.0 F)
Feb31.1 C (88.0 F)-23.3 C (-9.9 F)24.4 C (75.9 F)-16.1 C (3.0 F)
Mar33.3 C (91.9 F)-17.2 C (1.0 F)33.3 C (91.9 F)-7.8 C (18.0 F)
Apr33.3 C (91.9 F)-9.4 C (15.1 F)28.3 C (82.9 F)0.0 C (32.0 F)
May35.0 C (95.0 F)-2.2 C (28.0 F)29.4 C (84.9 F)1.7 C (35.1 F)
Jun38.9 C (102.0 F)4.4 C (39.9 F)33.3 C (91.9 F)11.7 C (53.1 F)
Jul41.7 C (107.1 F)7.8 C (46.0 F)36.7 C (98.1 F)17.2 C (63.0 F)
Aug42.8 C (109.0 F)7.2 C (45.0 F)38.3 C (100.9 F)13.9 C (57.0 F)
Sep39.4 C (102.9 F)-0.6 C (30.9 F)38.9 C (102.0 F)10.0 C (50.0 F)
Oct35.6 C (96.1 F)-8.9 C (16.0 F)33.9 C (93.0 F)14.4 C (57.9 F)
Nov29.4 C (84.9 F)-17.2 C (1.0 F)n/an/a
Dec24.4 C (75.9 F)-21.1 C (-6.0 F)n/an/a

Which Years Hold Standing Records

1,464 standing records
Standing records at Alton by the year they were set 1,464 records at Alton still stand. 2000 holds the most, with 63. 0204060801962: 101963: 481964: 321965: 341966: 431967: 491968: 261969: 331970: 381971: 271972: 391973: 261974: 421975: 311976: 521977: 281978: 331979: 261980: 341981: 371982: 391983: 171984: 141994: 81995: 311996: 341997: 321998: 471999: 312000: 632001: 342002: 282003: 222004: 372005: 242006: 342007: 232008: 332009: 232010: 282011: 292012: 252013: 142014: 82023: 142024: 252025: 292026: 301962196719721977198219962001200620112024
1,464 records at Alton still stand. 2000 holds the most, with 63.
Standing records at Alton by the year they were set
Year setStanding records
196210
196348
196432
196534
196643
196749
196826
196933
197038
197127
197239
197326
197442
197531
197652
197728
197833
197926
198034
198137
198239
198317
198414
19948
199531
199634
199732
199847
199931
200063
200134
200228
200322
200437
200524
200634
200723
200833
200923
201028
201129
201225
201314
20148
202314
202425
202529
202630

All-Time Record Progression

5 new records
When Alton set new all-time records 5 all-time records were set at Alton between 8 February 1980 and 15 January 2024. Each dot is a new record. Record daily snowfallRecord daily precipitationRecord low maximum temperatureRecord high maximum temperature8 February 1980: Record daily snowfall 31.8 cm (12.5 in)3 December 1982: Record daily precipitation 212.1 mm (8.4 in)11 February 2011: Record low maximum temperature -11.1 C (12.0 F)4 August 2011: Record high maximum temperature 42.8 C (109.0 F)15 January 2024: Record low maximum temperature -14.4 C (6.1 F)19801990200020102020
5 all-time records were set at Alton between 8 February 1980 and 15 January 2024. Each dot is a new record.
When Alton set new all-time records
DateKindDetail
1980-02-08Record daily snowfallRecord daily snowfall 31.8 cm (12.5 in)
1982-12-03Record daily precipitationRecord daily precipitation 212.1 mm (8.4 in)
2011-02-11Record low maximum temperatureRecord low maximum temperature -11.1 C (12.0 F)
2011-08-04Record high maximum temperatureRecord high maximum temperature 42.8 C (109.0 F)
2024-01-15Record low maximum temperatureRecord low maximum temperature -14.4 C (6.1 F)

Wettest Day of Each Month

Dec: 212.1 mm (8.4 in)
Record daily precipitation for each month at Alton The wettest day on record for each calendar month at Alton. The most was 212.1 mm (8.4 in) on 3 December 1982. 0100200300 Jan: 95.3 mm (3.8 in), 31 January 1982 Jan Feb: 94.2 mm (3.7 in), 13 February 2007 Feb Mar: 155.4 mm (6.1 in), 19 March 2008 Mar Apr: 120.7 mm (4.8 in), 5 April 2025 Apr May: 116.8 mm (4.6 in), 12 May 1950 May Jun: 93.2 mm (3.7 in), 18 June 2000 Jun Jul: 85.1 mm (3.4 in), 19 July 2002 Jul Aug: 106.7 mm (4.2 in), 23 August 2019 Aug Sep: 121.2 mm (4.8 in), 23 September 2006 Sep Oct: 94.5 mm (3.7 in), 30 October 2009 Oct Nov: 121.2 mm (4.8 in), 17 November 1958 Nov Dec: 212.1 mm (8.4 in), 3 December 1982 Dec
The wettest day on record for each calendar month at Alton. The most was 212.1 mm (8.4 in) on 3 December 1982.
Record daily precipitation for each month at Alton
MonthRecord daily precipitation (mm)Date
Jan95.3 mm (3.8 in)31 January 1982
Feb94.2 mm (3.7 in)13 February 2007
Mar155.4 mm (6.1 in)19 March 2008
Apr120.7 mm (4.8 in)5 April 2025
May116.8 mm (4.6 in)12 May 1950
Jun93.2 mm (3.7 in)18 June 2000
Jul85.1 mm (3.4 in)19 July 2002
Aug106.7 mm (4.2 in)23 August 2019
Sep121.2 mm (4.8 in)23 September 2006
Oct94.5 mm (3.7 in)30 October 2009
Nov121.2 mm (4.8 in)17 November 1958
Dec212.1 mm (8.4 in)3 December 1982

Period of Record Coverage

1962 to 2026
Days with data per year at Alton 48 years of record at Alton, 1962 to 2026. 19 years have data for under 90 percent of days and are left out of rankings: 1962, 1965, 1966, 1967, 1968, 1979, 1980, 1981 and others. 1962: 90 of 365 days1963: 335 of 365 days1964: 330 of 366 days1965: 318 of 365 days1966: 322 of 365 days1967: 292 of 365 days1968: 278 of 366 days1969: 338 of 365 days1970: 344 of 365 days1971: 345 of 365 days1972: 352 of 366 days1973: 354 of 365 days1974: 348 of 365 days1975: 339 of 365 days1976: 361 of 366 days1977: 359 of 365 days1978: 357 of 365 days1979: 326 of 365 days1980: 163 of 366 days1981: 297 of 365 days1982: 326 of 365 days1983: 101 of 365 days1984: 103 of 366 days1994: 152 of 365 days1995: 364 of 365 days1996: 358 of 366 days1997: 354 of 365 days1998: 365 of 365 days1999: 365 of 365 days2000: 365 of 366 days2001: 363 of 365 days2002: 365 of 365 days2003: 364 of 365 days2004: 366 of 366 days2005: 360 of 365 days2006: 352 of 365 days2007: 356 of 365 days2008: 337 of 366 days2009: 301 of 365 days2010: 260 of 365 days2011: 329 of 365 days2012: 208 of 366 days2013: 139 of 365 days2014: 71 of 365 days2023: 192 of 365 days2024: 366 of 366 days2025: 365 of 365 days2026: 271 of 365 days1970198020002010
48 years of record at Alton, 1962 to 2026. 19 years have data for under 90 percent of days and are left out of rankings: 1962, 1965, 1966, 1967, 1968, 1979, 1980, 1981 and others.
Days with data per year at Alton
YearDays with dataShare of yearComplete
19629025%No
196333592%Yes
196433090%Yes
196531887%No
196632288%No
196729280%No
196827876%No
196933893%Yes
197034494%Yes
197134595%Yes
197235296%Yes
197335497%Yes
197434895%Yes
197533993%Yes
197636199%Yes
197735998%Yes
197835798%Yes
197932689%No
198016345%No
198129781%No
198232689%No
198310128%No
198410328%No
199415242%No
1995364100%Yes
199635898%Yes
199735497%Yes
1998365100%Yes
1999365100%Yes
2000365100%Yes
200136399%Yes
2002365100%Yes
2003364100%Yes
2004366100%Yes
200536099%Yes
200635296%Yes
200735698%Yes
200833792%Yes
200930182%No
201026071%No
201132990%Yes
201220857%No
201313938%No
20147119%No
202319253%No
2024366100%Yes
2025365100%Yes
202627174%No

Latest Records

20
Latest records at Alton
DateStationRecordValueBeat old record byOld record stoodSignificance
2 October 2026Alton, USdaily rain (Provisional)38.9 mm (1.5 in)30.5 mm (1.2 in)4 years29 of 100 (Routine)
2 October 2026Alton, USdaily high min (Provisional)19.4 C (66.9 F)1.1 C (2.0 F)12 years10 of 100 (Routine)
21 September 2026Alton, USdaily high max (Provisional)36.7 C (98.1 F)1.7 C (3.1 F)25 years16 of 100 (Routine)
20 September 2026Alton, USdaily high max (Provisional)37.2 C (99.0 F)2.2 C (4.0 F)25 years18 of 100 (Routine)
18 September 2026Alton, USdaily high max (Provisional)37.2 C (99.0 F)2.8 C (5.0 F)53 years28 of 100 (Routine)
16 September 2026Alton, USdaily high min (Provisional)21.7 C (71.1 F)1.7 C (3.1 F)53 years25 of 100 (Routine)
16 September 2026Alton, USdaily high max (Provisional)37.2 C (99.0 F)2.8 C (5.0 F)0 years12 of 100 (Routine)
15 September 2026Alton, USdaily high min (Provisional)20.6 C (69.1 F)0.6 C (1.1 F)60 years25 of 100 (Routine)
14 September 2026Alton, USdaily high min (Provisional)20.6 C (69.1 F)0.6 C (1.1 F)60 years25 of 100 (Routine)
11 September 2026Alton, USdaily high min (Tie, Provisional)21.1 C (70.0 F)tie25 years3 of 100 (Routine)
10 September 2026Alton, USdaily high max (Provisional)38.9 C (102.0 F)1.1 C (2.0 F)45 years21 of 100 (Routine)
10 September 2026Alton, USdaily high min (Tie, Provisional)21.7 C (71.1 F)tie25 years3 of 100 (Routine)
6 September 2026Alton, USdaily high max (Provisional)38.9 C (102.0 F)2.2 C (4.0 F)43 years23 of 100 (Routine)
6 September 2026Alton, USdaily high min (Provisional)21.1 C (70.0 F)0.5 C (0.9 F)56 years23 of 100 (Routine)
5 September 2026Alton, USdaily high max (Tie, Provisional)37.8 C (100.0 F)tie27 years3 of 100 (Routine)
5 September 2026Alton, USdaily high min (Tie, Provisional)21.1 C (70.0 F)tie27 years3 of 100 (Routine)
17 August 2026Alton, USdaily high max (Tie, Provisional)38.3 C (100.9 F)tie25 years3 of 100 (Routine)
14 August 2026Alton, USdaily high min (Tie)23.3 C (73.9 F)tie16 years2 of 100 (Routine)
2 August 2026Alton, USdaily low max23.3 C (73.9 F)2.3 C (4.1 F)49 years26 of 100 (Routine)
29 July 2026Alton, USdaily high min25.0 C (77.0 F)0.6 C (1.1 F)3 years8 of 100 (Routine)

Climate Trend

26 complete years, 1963 to 2025
Annual mean temperature at Alton as warming stripes, 1963 to 2025 One stripe for each of 26 complete years at Alton, 1963 to 2025. Blue stripes are years cooler than the station's own mean of 13.8 C (56.8 F); red stripes are warmer. The coolest year was 2008, at 12.5 C (54.5 F), and the warmest was 2024, at 15.1 C (59.2 F). The strongest colour marks a difference of 1.4 C (2.5 F). 1963: 13.8 C, +0.1 C from the station mean1965: 14.4 C, +0.6 C from the station mean1969: 13.3 C, -0.5 C from the station mean1970: 13.7 C, 0.0 C from the station mean1971: 14.3 C, +0.5 C from the station mean1972: 13.6 C, -0.1 C from the station mean1973: 14.2 C, +0.5 C from the station mean1974: 13.8 C, 0.0 C from the station mean1976: 13.0 C, -0.8 C from the station mean1977: 13.8 C, +0.1 C from the station mean1978: 12.8 C, -1.0 C from the station mean1995: 13.2 C, -0.6 C from the station mean1996: 12.6 C, -1.2 C from the station mean1998: 14.9 C, +1.2 C from the station mean1999: 14.4 C, +0.7 C from the station mean2000: 13.9 C, +0.2 C from the station mean2001: 14.2 C, +0.4 C from the station mean2002: 13.6 C, -0.2 C from the station mean2003: 13.1 C, -0.7 C from the station mean2004: 13.3 C, -0.4 C from the station mean2005: 14.0 C, +0.2 C from the station mean2006: 13.9 C, +0.1 C from the station mean2007: 14.1 C, +0.3 C from the station mean2008: 12.5 C, -1.3 C from the station mean2024: 15.1 C, +1.3 C from the station mean2025: 14.3 C, +0.6 C from the station mean1963197019801990200020102020
One stripe for each of 26 complete years at Alton, 1963 to 2025. Blue stripes are years cooler than the station's own mean of 13.8 C (56.8 F); red stripes are warmer. The coolest year was 2008, at 12.5 C (54.5 F), and the warmest was 2024, at 15.1 C (59.2 F). The strongest colour marks a difference of 1.4 C (2.5 F).
Annual mean temperature at Alton as warming stripes, 1963 to 2025
YearAnnual mean temperatureDifference from the station mean
196313.8 C+0.06 C
196514.4 C+0.60 C
196913.3 C-0.49 C
197013.7 C-0.01 C
197114.3 C+0.50 C
197213.6 C-0.14 C
197314.2 C+0.47 C
197413.8 C0.00 C
197613.0 C-0.75 C
197713.8 C+0.08 C
197812.8 C-0.97 C
199513.2 C-0.60 C
199612.6 C-1.16 C
199814.9 C+1.18 C
199914.4 C+0.67 C
200013.9 C+0.16 C
200114.2 C+0.44 C
200213.6 C-0.17 C
200313.1 C-0.68 C
200413.3 C-0.42 C
200514.0 C+0.22 C
200613.9 C+0.10 C
200714.1 C+0.35 C
200812.5 C-1.27 C
202415.1 C+1.35 C
202514.3 C+0.57 C

This station does not have enough complete years (30 are needed) to fit a temperature trend.

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

1940 to 2026
Yearly extremes at Alton: the record and the median year
MeasureRecordYear of the recordMedian yearYears with a value
Hottest day (TXx)42.8 C (109.0 F)201137.8 C (100.0 F)48
Coldest night (TNn)-27.8 C (-18.0 F)1977-17.8 C (0.0 F)48
Wettest day (Rx1day)212.1 mm (8.4 in)198274.2 mm (2.9 in)73
Wettest five days (Rx5day)334.8 mm (13.2 in)1982108.0 mm (4.3 in)72
Longest dry spell (CDD)63 days201021 days73

Hottest day (TXx)

Hottest day (TXx) at Alton by year The hottest day of the year at Alton, 1940 to 2026. The record is 42.8 C (109.0 F) in 2011, marked on the chart; the median year is 37.8 C (100.0 F). 20253035404519401960198020002020Record: 42.8 C (109.0 F) in 2011
The hottest day of the year at Alton, 1940 to 2026. The record is 42.8 C (109.0 F) in 2011, marked on the chart; the median year is 37.8 C (100.0 F).
Hottest day (TXx) at Alton by year
YearHottest day (TXx)
1940n/a
1941n/a
1942n/a
1945n/a
1946n/a
1948n/a
1949n/a
1950n/a
1951n/a
1952n/a
1953n/a
1954n/a
1955n/a
1956n/a
1957n/a
1958n/a
1959n/a
1960n/a
1961n/a
196230.6 C (87.1 F)
196338.9 C (102.0 F)
196440.0 C (104.0 F)
196537.8 C (100.0 F)
196640.6 C (105.1 F)
196735.6 C (96.1 F)
196835.0 C (95.0 F)
196940.0 C (104.0 F)
197037.2 C (99.0 F)
197137.2 C (99.0 F)
197236.7 C (98.1 F)
197336.7 C (98.1 F)
197437.8 C (100.0 F)
197537.8 C (100.0 F)
197636.7 C (98.1 F)
197737.8 C (100.0 F)
197838.9 C (102.0 F)
197935.0 C (95.0 F)
198037.8 C (100.0 F)
198136.7 C (98.1 F)
198236.7 C (98.1 F)
198339.4 C (102.9 F)
198431.7 C (89.1 F)
199435.0 C (95.0 F)
199536.7 C (98.1 F)
199636.7 C (98.1 F)
199738.9 C (102.0 F)
199838.3 C (100.9 F)
199938.9 C (102.0 F)
200040.6 C (105.1 F)
200138.3 C (100.9 F)
200235.6 C (96.1 F)
200336.7 C (98.1 F)
200435.0 C (95.0 F)
200537.8 C (100.0 F)
200638.3 C (100.9 F)
200739.4 C (102.9 F)
200836.7 C (98.1 F)
200935.0 C (95.0 F)
201037.8 C (100.0 F)
201142.8 C (109.0 F)
201241.7 C (107.1 F)
201335.6 C (96.1 F)
201424.4 C (75.9 F)
2017n/a
2018n/a
2019n/a
2020n/a
2021n/a
2022n/a
202338.9 C (102.0 F)
202436.1 C (97.0 F)
202537.8 C (100.0 F)
202638.9 C (102.0 F)

Coldest night (TNn)

Coldest night (TNn) at Alton by year The coldest night of the year at Alton, 1940 to 2026. The record is -27.8 C (-18.0 F) in 1977, marked on the chart; the median year is -17.8 C (0.0 F). -30-20-10019401960198020002020Record: -27.8 C (-18.0 F) in 1977
The coldest night of the year at Alton, 1940 to 2026. The record is -27.8 C (-18.0 F) in 1977, marked on the chart; the median year is -17.8 C (0.0 F).
Coldest night (TNn) at Alton by year
YearColdest night (TNn)
1940n/a
1941n/a
1942n/a
1945n/a
1946n/a
1948n/a
1949n/a
1950n/a
1951n/a
1952n/a
1953n/a
1954n/a
1955n/a
1956n/a
1957n/a
1958n/a
1959n/a
1960n/a
1961n/a
1962-19.4 C (-2.9 F)
1963-22.8 C (-9.0 F)
1964-17.8 C (0.0 F)
1965-16.7 C (1.9 F)
1966-19.4 C (-2.9 F)
1967-16.1 C (3.0 F)
1968-16.1 C (3.0 F)
1969-15.6 C (3.9 F)
1970-21.1 C (-6.0 F)
1971-19.4 C (-2.9 F)
1972-17.8 C (0.0 F)
1973-17.8 C (0.0 F)
1974-17.2 C (1.0 F)
1975-14.4 C (6.1 F)
1976-21.1 C (-6.0 F)
1977-27.8 C (-18.0 F)
1978-17.8 C (0.0 F)
1979-17.8 C (0.0 F)
1980-18.3 C (-0.9 F)
1981-20.0 C (-4.0 F)
1982-23.3 C (-9.9 F)
1983-5.0 C (23.0 F)
1984-15.0 C (5.0 F)
1994-7.2 C (19.0 F)
1995-17.8 C (0.0 F)
1996-22.8 C (-9.0 F)
1997-21.1 C (-6.0 F)
1998-14.4 C (6.1 F)
1999-17.8 C (0.0 F)
2000-16.1 C (3.0 F)
2001-18.3 C (-0.9 F)
2002-15.6 C (3.9 F)
2003-18.9 C (-2.0 F)
2004-20.0 C (-4.0 F)
2005-13.9 C (7.0 F)
2006-17.8 C (0.0 F)
2007-16.7 C (1.9 F)
2008-16.7 C (1.9 F)
2009-15.6 C (3.9 F)
2010-17.8 C (0.0 F)
2011-21.1 C (-6.0 F)
2012-12.2 C (10.0 F)
2013-16.1 C (3.0 F)
2014-21.1 C (-6.0 F)
2017n/a
2018n/a
2019n/a
2020n/a
2021n/a
2022n/a
2023-8.9 C (16.0 F)
2024-19.4 C (-2.9 F)
2025-18.3 C (-0.9 F)
2026-18.9 C (-2.0 F)

Wettest day (Rx1day)

Wettest day (Rx1day) at Alton by year The wettest day of the year at Alton, 1940 to 2026. The record is 212.1 mm (8.4 in) in 1982, marked on the chart; the median year is 74.2 mm (2.9 in). 010020030019401960198020002020Record: 212.1 mm (8.4 in) in 1982
The wettest day of the year at Alton, 1940 to 2026. The record is 212.1 mm (8.4 in) in 1982, marked on the chart; the median year is 74.2 mm (2.9 in).
Wettest day (Rx1day) at Alton by year
YearWettest day (Rx1day)
194054.9 mm (2.2 in)
194171.4 mm (2.8 in)
194223.4 mm (0.9 in)
194573.7 mm (2.9 in)
194668.1 mm (2.7 in)
194857.9 mm (2.3 in)
194973.7 mm (2.9 in)
1950116.8 mm (4.6 in)
195171.1 mm (2.8 in)
195276.2 mm (3.0 in)
195340.6 mm (1.6 in)
195458.7 mm (2.3 in)
195562.2 mm (2.4 in)
195668.3 mm (2.7 in)
195789.9 mm (3.5 in)
1958121.2 mm (4.8 in)
195957.7 mm (2.3 in)
196059.9 mm (2.4 in)
196191.4 mm (3.6 in)
196263.8 mm (2.5 in)
196378.7 mm (3.1 in)
196480.8 mm (3.2 in)
196594.0 mm (3.7 in)
196685.3 mm (3.4 in)
196764.8 mm (2.6 in)
196854.6 mm (2.1 in)
196991.9 mm (3.6 in)
197086.4 mm (3.4 in)
197176.2 mm (3.0 in)
197266.0 mm (2.6 in)
1973116.1 mm (4.6 in)
197475.7 mm (3.0 in)
1975114.3 mm (4.5 in)
197687.9 mm (3.5 in)
1977111.3 mm (4.4 in)
197852.1 mm (2.1 in)
197977.0 mm (3.0 in)
198041.1 mm (1.6 in)
198148.3 mm (1.9 in)
1982212.1 mm (8.4 in)
198350.3 mm (2.0 in)
198434.3 mm (1.4 in)
1994102.4 mm (4.0 in)
199552.8 mm (2.1 in)
199697.0 mm (3.8 in)
1997108.2 mm (4.3 in)
199861.0 mm (2.4 in)
199964.8 mm (2.6 in)
200093.2 mm (3.7 in)
200152.3 mm (2.1 in)
200285.1 mm (3.4 in)
200399.1 mm (3.9 in)
200465.5 mm (2.6 in)
200553.3 mm (2.1 in)
2006121.2 mm (4.8 in)
200794.2 mm (3.7 in)
2008155.4 mm (6.1 in)
200994.5 mm (3.7 in)
201075.4 mm (3.0 in)
201196.3 mm (3.8 in)
201255.9 mm (2.2 in)
201350.8 mm (2.0 in)
20140.8 mm (0.03 in)
2017100.3 mm (3.9 in)
201863.5 mm (2.5 in)
2019106.7 mm (4.2 in)
202068.6 mm (2.7 in)
202174.2 mm (2.9 in)
202286.4 mm (3.4 in)
202367.8 mm (2.7 in)
202474.2 mm (2.9 in)
2025120.7 mm (4.8 in)
202662.2 mm (2.4 in)

Wettest five days (Rx5day)

Wettest five days (Rx5day) at Alton by year The wettest five days of the year at Alton, 1940 to 2026. The record is 334.8 mm (13.2 in) in 1982, marked on the chart; the median year is 108.0 mm (4.3 in). 010020030040019401960198020002020Record: 334.8 mm (13.2 in) in 1982
The wettest five days of the year at Alton, 1940 to 2026. The record is 334.8 mm (13.2 in) in 1982, marked on the chart; the median year is 108.0 mm (4.3 in).
Wettest five days (Rx5day) at Alton by year
YearWettest five days (Rx5day)
194091.5 mm (3.6 in)
194198.3 mm (3.9 in)
194239.9 mm (1.6 in)
1945132.8 mm (5.2 in)
1946n/a
194858.4 mm (2.3 in)
194973.7 mm (2.9 in)
1950233.7 mm (9.2 in)
195188.9 mm (3.5 in)
1952101.6 mm (4.0 in)
195361.0 mm (2.4 in)
195483.4 mm (3.3 in)
195594.0 mm (3.7 in)
195691.1 mm (3.6 in)
1957151.5 mm (6.0 in)
1958242.6 mm (9.6 in)
195989.6 mm (3.5 in)
196087.6 mm (3.4 in)
1961173.2 mm (6.8 in)
196294.0 mm (3.7 in)
1963148.0 mm (5.8 in)
1964177.1 mm (7.0 in)
1965111.0 mm (4.4 in)
1966136.1 mm (5.4 in)
1967122.5 mm (4.8 in)
1968112.3 mm (4.4 in)
196999.7 mm (3.9 in)
1970122.0 mm (4.8 in)
1971154.9 mm (6.1 in)
1972122.0 mm (4.8 in)
1973193.6 mm (7.6 in)
1974123.4 mm (4.9 in)
1975175.3 mm (6.9 in)
197695.5 mm (3.8 in)
1977161.6 mm (6.4 in)
197887.1 mm (3.4 in)
1979113.0 mm (4.4 in)
198042.6 mm (1.7 in)
198162.7 mm (2.5 in)
1982334.8 mm (13.2 in)
198379.3 mm (3.1 in)
198465.4 mm (2.6 in)
1994182.5 mm (7.2 in)
199589.6 mm (3.5 in)
1996102.1 mm (4.0 in)
1997122.9 mm (4.8 in)
1998102.0 mm (4.0 in)
199983.8 mm (3.3 in)
2000142.2 mm (5.6 in)
2001114.0 mm (4.5 in)
2002104.9 mm (4.1 in)
2003131.2 mm (5.2 in)
2004143.9 mm (5.7 in)
200588.3 mm (3.5 in)
2006147.9 mm (5.8 in)
200795.0 mm (3.7 in)
2008215.9 mm (8.5 in)
200995.7 mm (3.8 in)
201081.5 mm (3.2 in)
2011294.7 mm (11.6 in)
201282.5 mm (3.2 in)
2013125.7 mm (4.9 in)
20140.8 mm (0.03 in)
2017158.9 mm (6.3 in)
2018140.2 mm (5.5 in)
2019139.2 mm (5.5 in)
2020130.6 mm (5.1 in)
202185.4 mm (3.4 in)
202286.4 mm (3.4 in)
202386.1 mm (3.4 in)
2024150.9 mm (5.9 in)
2025203.8 mm (8.0 in)
202682.5 mm (3.2 in)

Longest dry spell (CDD)

Longest dry spell (CDD) at Alton by year The longest dry spell of the year at Alton, 1940 to 2026. The record is 63 days in 2010, marked on the chart; the median year is 21 days. 02040608019401960198020002020Record: 63 days in 2010
The longest dry spell of the year at Alton, 1940 to 2026. The record is 63 days in 2010, marked on the chart; the median year is 21 days.
Longest dry spell (CDD) at Alton by year
YearLongest dry spell (CDD)
194026 days
194118 days
194218 days
194514 days
19461 day
194820 days
194916 days
195026 days
195115 days
195223 days
195331 days
195418 days
195529 days
195618 days
195721 days
195812 days
195920 days
196016 days
196122 days
196220 days
196344 days
196439 days
196525 days
196631 days
196736 days
196819 days
196922 days
197023 days
197127 days
197216 days
197315 days
197425 days
197519 days
197641 days
197719 days
197825 days
197925 days
198023 days
198131 days
198216 days
198327 days
198412 days
199416 days
199523 days
199619 days
199715 days
199832 days
199920 days
200019 days
200115 days
200218 days
200314 days
200433 days
200521 days
200618 days
200727 days
200816 days
200926 days
201063 days
201128 days
201216 days
201327 days
201423 days
201719 days
201819 days
201924 days
202024 days
202115 days
202239 days
202313 days
202432 days
202517 days
202625 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

26 years with a frost

Across 26 years with a frost, the median last spring frost at Alton falls on 17 April and the median first autumn frost on 16 October, which leaves a median of 183 days between them.

Fitted over all years, the growing season changes by +1.5 days per decade at this station.

Frost dates and growing season at Alton
MeasureMedian, all yearsEarliest periodRecent period (1963 to 2025)Recent against earliestFitted trend
Last spring frost17 Apriln/a17 Apriln/a-0.5 days per decade
First autumn frost16 Octobern/a16 Octobern/a+1.0 days per decade
Growing days183 daysn/a183 daysn/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

51 years, 1941 to 2024

A day with at least 78.3 mm (3.1 in) of rain is expected about once in 2 years. A day with at least 188.6 mm (7.4 in) of rain is expected about once in 100 years.

Rainfall return levels at Alton: the daily rain expected about once in a given number of years
Expected about once inA day with at leastNote
2 years78.3 mm (3.1 in)
5 years101.7 mm (4.0 in)
10 years119.3 mm (4.7 in)
25 years144.5 mm (5.7 in)
50 years165.5 mm (6.5 in)
100 years188.6 mm (7.4 in)Longer than the 51 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, 51 years of values from 1941 to 2024.

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: 212.1 mm (8.4 in) in 1982; 155.4 mm (6.1 in) in 2008; 121.2 mm (4.8 in) in 1958.

Download the Data

  • Data for Alton standing records by year: CSV or JSON. Field meanings are on the data page.
  • 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 2026-10-12 (12 October 2026). Records are computed by this site and are not official.

Data as of . Last revised (2026-10-13).