May, IL climate
May has chilly winters and warm summers. A typical July afternoon reaches 86°, a January night drops to 20°, and about 15 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in May feels like
Winter
Spring
Summer
Fall
May weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 36° | 20° | 2.4" | 5.1" | 9 | 9 | 21° – 39° |
| February | 41° | 24° | 2.0" | 2.6" | 8 | 6 | 20° – 42° |
| March | 52° | 33° | 2.9" | 2.6" | 11 | 2 | 35° – 56° |
| April | 65° | 42° | 4.4" | 0.5" | 12 | 0 | 46° – 60° |
| May | 75° | 53° | 4.8" | 0 | 13 | 0 | 59° – 72° |
| June | 84° | 62° | 4.8" | 0 | 11 | 0 | 68° – 76° |
| July | 86° | 65° | 3.7" | 0 | 9 | 0 | 71° – 83° |
| August | 85° | 63° | 3.3" | 0 | 8 | 0 | 69° – 80° |
| September | 80° | 55° | 3.1" | 0 | 8 | 0 | 62° – 72° |
| October | 67° | 44° | 3.4" | 0.1" | 9 | 0 | 51° – 61° |
| November | 52° | 34° | 3.3" | 0.9" | 10 | 1 | 35° – 50° |
| December | 40° | 25° | 2.4" | 2.7" | 9 | 4 | 19° – 41° |
| Year | 64° | 43° | 40.4" | 14.5" | 116 | 22 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in May
May gets 40 inches of rain and melted snow a year. May is the wettest month and February the driest. Rain or snow falls on about 116 days a year. Snow covers the ground about 22 days of the year.
About 188 frost-free days a year
In half of years the last 32° night comes by April 17 and the first one by October 23. That leaves about 188 frost-free days for gardens, longer than 62% of U.S. towns.
Heating and cooling a home in May
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In May, 82% of that work is heating and 18% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
May and its neighbors
May borders 5 towns with climate data. January nights across them vary by 0.5°. Stonington has the coldest January nights (20°) and Locust the hottest July afternoons (86°). May’s January low is 20° and its July high 86°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How May compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in May averaged 1.0° warmer than the 1900s. The biggest change is in December (+2.1°). The shift is smaller than in 69% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at May’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. December swings the most: between 1991 and 2020 its average temperature ranged from 19° to 41°. June is the most reliable, staying within 8°.
Common questions about May’s climate
What is the coldest month in May?
January, with a typical high of 36° and a low of 20°.
What is the hottest month in May?
July, with a typical high of 86° and a low of 65°. About 34 days a year reach 90°.
How much snow does May get?
About 15 inches in a normal winter, most of it in January.
When is the first frost in May?
In half of years the first 32° night comes by October 23, and the last spring frost by April 17.
What is the rainiest month in May?
May, with 4.8 inches of rain and melted snow. The year totals 40 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for May itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Pana, IL (15 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.