Alton Weather in May
Average highs run from 60°F on May 1 to 69°F on May 31, and lows from 36°F to 45°F. Normal precipitation for the month is 3.47 in over about 14 wet days.
May day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
May at a glance
- Average high
- 65°F
- Average low
- 41°F
- Precipitation
- 3.47 in
- Record high
- 96°FMay 22, 1992
- Record low
- 25°FMay 2, 2008
- Chance of a freeze
- 87%
- Daylight
- 14 h 17 min to 15 h 22 min
- Cloud cover
- 71%
- Humidity
- 80%
- Dew point
- 46°F
- Wind
- 4.5 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation; snow means at least 0.1 inch of snowfall.
| Date | Normal high | Normal low | Record high | Record low | Chance wet | Chance of snow |
|---|---|---|---|---|---|---|
| May 1 | 60°F | 36°F | 82°F 1996 | 27°F 2000 | 44% | 2% |
| May 2 | 60°F | 36°F | 90°F 2001 | 25°F 2008 | 44% | 1% |
| May 3 | 61°F | 37°F | 91°F 2001 | 27°F 2000 | 44% | 1% |
| May 4 | 61°F | 37°F | 84°F 2001 | 28°F 1986 | 44% | 1% |
| May 5 | 61°F | 37°F | 80°F 1960 | 30°F 1976 | 44% | 1% |
| May 6 | 62°F | 38°F | 81°F 1960 | 28°F 2020 | 44% | 1% |
| May 7 | 62°F | 38°F | 81°F 2015 | 28°F 1966 | 44% | 1% |
| May 8 | 62°F | 38°F | 87°F 1957 | 27°F 1966 | 44% | 1% |
| May 9 | 63°F | 39°F | 91°F 1979 | 29°F 1997 | 44% | 1% |
| May 10 | 63°F | 39°F | 87°F 2007 | 32°F 2024 | 44% | 1% |
| May 11 | 63°F | 39°F | 83°F 2001 | 28°F 1956 | 44% | 0% |
| May 12 | 64°F | 40°F | 86°F 2022 | 31°F 2018 | 44% | 0% |
| May 13 | 64°F | 40°F | 81°F 1991 | 27°F 2005 | 44% | 0% |
| May 14 | 64°F | 40°F | 91°F 2022 | 31°F 2005 | 45% | 0% |
| May 15 | 65°F | 41°F | 85°F 2004 | 31°F 1999 | 45% | 0% |
| May 16 | 65°F | 41°F | 84°F 1998 | 31°F 2003 | 45% | 0% |
| May 17 | 65°F | 41°F | 88°F 1977 | 33°F 1957 | 45% | 0% |
| May 18 | 65°F | 41°F | 92°F 2017 | 31°F 1983 | 45% | 0% |
| May 19 | 66°F | 42°F | 89°F 1962 | 32°F 1991 | 45% | 0% |
| May 20 | 66°F | 42°F | 87°F 2026 | 31°F 2002 | 45% | 0% |
| May 21 | 66°F | 42°F | 92°F 1992 | 34°F 1974 | 45% | 0% |
| May 22 | 66°F | 43°F | 96°F 1992 | 33°F 2007 | 44% | 0% |
| May 23 | 67°F | 43°F | 91°F 1992 | 36°F 2015 | 44% | 0% |
| May 24 | 67°F | 43°F | 91°F 1964 | 32°F 1956 | 44% | 0% |
| May 25 | 67°F | 44°F | 92°F 2007 | 31°F 1956 | 44% | 0% |
| May 26 | 67°F | 44°F | 88°F 2010 | 32°F 2009 | 44% | 0% |
| May 27 | 68°F | 44°F | 87°F 1959 | 31°F 1969 | 44% | 0% |
| May 28 | 68°F | 44°F | 91°F 2023 | 33°F 1994 | 44% | 0% |
| May 29 | 68°F | 45°F | 88°F 1978 | 33°F 1970 | 44% | 0% |
| May 30 | 68°F | 45°F | 88°F 1998 | 36°F 1974 | 44% | 0% |
| May 31 | 69°F | 45°F | 91°F 1987 | 33°F 2026 | 44% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (EDT).
- May 1
- sunrise 5:24 AM, sunset 7:41 PM
- May 31
- sunrise 4:52 AM, sunset 8:14 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USW00094644 (Old Town 2 W), public domain. Records: NOAA GHCN-Daily, station USW00014606, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.