Denison, IL climate
Denison has chilly winters and warm summers. A typical July afternoon reaches 88°, a January night drops to 23°, and about 16 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Denison feels like
Winter
Spring
Summer
Fall
Denison 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 | 39° | 23° | 3.4" | 3.8" | 10 | 7 | 24° – 42° |
| February | 44° | 26° | 2.7" | 4.2" | 9 | 4 | 23° – 44° |
| March | 55° | 35° | 3.9" | 1.8" | 10 | 1 | 37° – 59° |
| April | 67° | 44° | 5.0" | 0 | 10 | 0 | 48° – 61° |
| May | 76° | 55° | 5.2" | 0 | 11 | 0 | 60° – 74° |
| June | 85° | 64° | 4.9" | 0 | 10 | 0 | 69° – 78° |
| July | 88° | 67° | 4.3" | 0 | 8 | 0 | 72° – 84° |
| August | 86° | 65° | 3.3" | 0 | 7 | 0 | 71° – 82° |
| September | 81° | 57° | 3.6" | 0 | 7 | 0 | 65° – 75° |
| October | 69° | 46° | 3.6" | 0.1" | 8 | 0 | 53° – 62° |
| November | 54° | 35° | 4.0" | 0.4" | 9 | 0 | 37° – 51° |
| December | 43° | 27° | 3.4" | 5.2" | 10 | 4 | 22° – 45° |
| Year | 66° | 45° | 47.3" | 15.5" | 108 | 17 |
“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 Denison
Denison gets 47 inches of rain and melted snow a year. May is the wettest month and February the driest. Rain or snow falls on about 108 days a year. Snow covers the ground about 17 days of the year.
About 200 frost-free days a year
In half of years the last 32° night comes by April 8 and the first one by October 26. That leaves about 200 frost-free days for gardens, longer than 72% of U.S. towns.
Heating and cooling a home in Denison
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Denison, 77% of that work is heating and 23% is cooling.
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.
Denison and its neighbors
Denison borders 5 towns with climate data. January nights across them vary by 0.2°. Lawrence has the coldest January nights (23°) and Vincennes the hottest July afternoons (88°). Denison’s January low is 23° and its July high 88°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Denison 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 Denison averaged 1.0° warmer than the 1900s. The biggest change is in February (+1.7°). The shift is smaller than in 74% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Denison’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 22° to 45°. June is the most reliable, staying within 9°.
Common questions about Denison’s climate
What is the coldest month in Denison?
January, with a typical high of 39° and a low of 23°.
What is the hottest month in Denison?
July, with a typical high of 88° and a low of 67°. About 41 days a year reach 90°.
How much snow does Denison get?
About 16 inches in a normal winter, most of it in December.
When is the first frost in Denison?
In half of years the first 32° night comes by October 26, and the last spring frost by April 8.
What is the rainiest month in Denison?
May, with 5.2 inches of rain and melted snow. The year totals 47 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Denison itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Lawrenceville 2wsw, IL (7 mi, snow) and Lawrenceville Intl Airport, IL (10 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.