Alton Weather in May
Average highs run from 72°F on May 1 to 80°F on May 31, and lows from 48°F to 58°F. Normal precipitation for the month is 5.57 in over about 10 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
- 76°F
- Average low
- 53°F
- Precipitation
- 5.57 in
- Record high
- 95°FMay 26, 2012
- Record low
- 31°FMay 16, 1997
- Chance of a freeze
- 13%
- Days of 90°F or more
- 1.3
- Daylight
- 13 h 42 min to 14 h 29 min
- Cloud cover
- 60%
- Humidity
- 80%
- Dew point
- 60°F
- Wind
- 4.3 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 | 72°F | 48°F | 83°F 2012 | 36°F 2014 | 33% | 0% |
| May 2 | 73°F | 49°F | 86°F 2020 | 35°F 2014 | 33% | 0% |
| May 3 | 73°F | 49°F | 82°F 2014 | 34°F 2005 | 33% | 0% |
| May 4 | 73°F | 49°F | 90°F 2014 | 33°F 2011 | 33% | 0% |
| May 5 | 73°F | 50°F | 88°F 2014 | 35°F 2013 | 33% | 0% |
| May 6 | 73°F | 50°F | 86°F 2012 | 40°F 2016 | 33% | 0% |
| May 7 | 74°F | 50°F | 85°F 2016 | 37°F 2026 | 33% | 0% |
| May 8 | 74°F | 51°F | 87°F 2000 | 41°F 2020 | 33% | 0% |
| May 9 | 74°F | 51°F | 88°F 2018 | 35°F 2020 | 32% | 0% |
| May 10 | 74°F | 51°F | 89°F 2022 | 40°F 2000 | 32% | 0% |
| May 11 | 74°F | 52°F | 89°F 2005 | 40°F 2020 | 32% | 0% |
| May 12 | 75°F | 52°F | 91°F 2022 | 37°F 2008 | 32% | 0% |
| May 13 | 75°F | 52°F | 89°F 2022 | 39°F 2021 | 32% | 0% |
| May 14 | 75°F | 53°F | 90°F 2013 | 37°F 2000 | 31% | 0% |
| May 15 | 75°F | 53°F | 86°F 2019 | 39°F 2014 | 31% | 0% |
| May 16 | 76°F | 53°F | 88°F 2012 | 31°F 1997 | 31% | 0% |
| May 17 | 76°F | 54°F | 87°F 2001 | 40°F 2011 | 30% | 0% |
| May 18 | 76°F | 54°F | 86°F 2012 | 38°F 2002 | 30% | 0% |
| May 19 | 76°F | 54°F | 89°F 2006 | 38°F 2002 | 30% | 0% |
| May 20 | 77°F | 54°F | 88°F 1998 | 42°F 2002 | 29% | 0% |
| May 21 | 77°F | 55°F | 88°F 1998 | 41°F 2002 | 29% | 0% |
| May 22 | 77°F | 55°F | 86°F 1998 | 39°F 2015 | 29% | 0% |
| May 23 | 78°F | 55°F | 93°F 2000 | 40°F 1997 | 28% | 0% |
| May 24 | 78°F | 56°F | 90°F 2000 | 43°F 2001 | 28% | 0% |
| May 25 | 78°F | 56°F | 90°F 2006 | 40°F 2001 | 28% | 0% |
| May 26 | 79°F | 56°F | 95°F 2012 | 47°F 1999 | 27% | 0% |
| May 27 | 79°F | 56°F | 92°F 2012 | 44°F 1999 | 27% | 0% |
| May 28 | 79°F | 57°F | 94°F 2012 | 46°F 2005 | 27% | 0% |
| May 29 | 80°F | 57°F | 93°F 2012 | 45°F 1997 | 26% | 0% |
| May 30 | 80°F | 57°F | 88°F 2018 | 41°F 2021 | 26% | 0% |
| May 31 | 80°F | 58°F | 93°F 1998 | 45°F 2021 | 26% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (CDT).
- May 1
- sunrise 6:12 AM, sunset 7:54 PM
- May 31
- sunrise 5:49 AM, sunset 8:18 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00230127 (Alton), public domain. Records: NOAA GHCN-Daily, station USW00053901, 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.