May weather in Alton, IL
The average temperature in Alton in May is 65.6°F (56.1°F–75.0°F). Average precipitation: 5.46 inches.
May is a spring month in Alton, and is warmer than the annual average of 55.7°F. Daily temperatures swing about 18.9°F between overnight low and afternoon high. Expect about 11 days with precipitation. Daylight averages about 14h 8m. For travel, May is a wet month.
Avg High
75.0°F
Avg Low
56.1°F
Precipitation
5.46 in
Daylight
14h 8m
May records in Alton
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| May 1 | 93.9°F (1953) | 34.0°F (1999) | 2.16 in (2017) |
| May 2 | 93.9°F (1952) | 36.0°F (1966) | 0.92 in (1983) |
| May 3 | 90.0°F (1949) | 34.0°F (1954) | 1.59 in (2024) |
| May 4 | 96.1°F (1952) | 34.0°F (1957) | 2.35 in (2017) |
| May 5 | 91.9°F (1952) | 37.0°F (1944) | 1.45 in (2003) |
| May 6 | 93.0°F (1946) | 37.0°F (1944) | 1.21 in (2022) |
| May 7 | 91.9°F (2007) | 37.9°F (1976) | 2.10 in (1971) |
| May 8 | 88.0°F (1986) | 37.0°F (1947) | 2.45 in (1961) |
| May 9 | 89.1°F (1986) | 35.1°F (1966) | 1.40 in (1961) |
| May 10 | 87.1°F (1963) | 32.0°F (1966) | 2.33 in (1949) |
| May 11 | 84.9°F (1944) | 39.9°F (1949) | 1.93 in (2007) |
| May 12 | 89.1°F (1944) | 39.0°F (1960) | 1.78 in (2010) |
| May 13 | 90.0°F (1956) | 39.0°F (1971) | 3.78 in (2002) |
| May 14 | 91.9°F (1949) | 39.9°F (1953) | 2.48 in (2004) |
| May 15 | 93.9°F (1944) | 43.0°F (1959) | 0.98 in (2004) |
| May 16 | 98.1°F (1944) | 42.1°F (1983) | 2.74 in (1990) |
| May 17 | 93.9°F (1944) | 42.1°F (1983) | 4.70 in (1995) |
| May 18 | 91.0°F (1964) | 41.0°F (2002) | 2.25 in (1995) |
| May 19 | 91.9°F (1944) | 41.0°F (2002) | 1.02 in (2018) |
| May 20 | 91.9°F (1944) | 43.0°F (1954) | 1.60 in (2025) |
| May 21 | 91.9°F (1962) | 43.0°F (2002) | 1.25 in (2013) |
| May 22 | 93.0°F (1987) | 43.0°F (2002) | 2.12 in (1949) |
| May 23 | 91.0°F (1950) | 43.0°F (1963) | 2.70 in (1944) |
| May 24 | 96.1°F (1953) | 45.0°F (1956) | 1.32 in (1971) |
| May 25 | 91.9°F (1953) | 44.1°F (1949) | 2.45 in (1960) |
| May 26 | 98.1°F (1953) | 41.0°F (1961) | 3.69 in (2008) |
| May 27 | 91.9°F (1977) | 35.1°F (1996) | 1.76 in (1893) |
| May 28 | 91.0°F (1972) | 41.0°F (1947) | 2.02 in (1944) |
| May 29 | 93.9°F (1953) | 39.9°F (1947) | 1.35 in (1982) |
| May 30 | 91.9°F (2011) | 45.0°F (1984) | 1.92 in (1991) |
| May 31 | 93.0°F (1946) | 42.1°F (1972) | 3.79 in (1974) |