Rock Island has cold, snowy winters and warm summers
A typical July afternoon reaches 85°, a January night drops to 14°, and about 36 inches of snow falls in a normal winter.
A year in Rock Island at a glance
Each month’s typical high and low, and what it brings.
What stands out about Rock Island’s climate
Read from where Rock Island sits among Illinois’s towns. The page puts what stands out first.
36 inches of snow, 37 of rain and melt
June is the wettest month and January the driest. Rain or snow falls on about 117 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
About 176 frost-free days a year
In half of years the last 32° night comes by April 24 and the first by October 18.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
What a year in Rock Island feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
Living with Rock Island’s climate
What the numbers mean for a garden, a driveway, a furnace and a free afternoon.
176 frost-free days. The last frost comes by Apr 24 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 18.
About 36" a winter over 11 days with an inch or more, most in January.
Months averaging under 55° run from October through April. Heating is 85% of the year’s heating-and-cooling load.
About 22 days a year reach 90°, and July afternoons average 85°.
The nicest months are May, June, August, September and October. 15 miles of trails are waiting.
Parks & trails →Normals are averages. Ice storms, nor’easters, floods and heat waves are on the natural hazards page.
Natural hazards →Rock Island and its neighbors
Rock Island Arsenal has the coldest January nights next door (14°) and Milan the hottest July afternoons (85°). Tap a town to see its climate.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Rock Island averaged 1.2° warmer than the 1900s. The biggest change is in March (+2.2°).
A smaller shift than in 55% of U.S. towns.
Change by month
How Rock Island compares
Against every U.S. town on TownTapestry, each counted once, with its place in Illinois.
Rock Island 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 | 30-yr range |
|---|---|---|---|---|---|---|
| January | 31° | 14° | 1.4" | 10.8" | 9 | 14° – 35° |
| February | 36° | 18° | 1.7" | 8.6" | 9 | 15° – 38° |
| March | 49° | 29° | 2.4" | 4.4" | 10 | 31° – 53° |
| April | 62° | 40° | 3.7" | 1.1" | 11 | 43° – 58° |
| May | 73° | 51° | 4.7" | 0 | 12 | 56° – 70° |
| June | 82° | 61° | 4.9" | 0 | 11 | 69° – 76° |
| July | 85° | 65° | 4.0" | 0 | 9 | 69° – 81° |
| August | 83° | 63° | 4.0" | 0 | 9 | 67° – 78° |
| September | 77° | 54° | 3.5" | 0 | 8 | 60° – 71° |
| October | 64° | 43° | 2.8" | 0.3" | 9 | 48° – 59° |
| November | 49° | 31° | 2.2" | 2.1" | 9 | 32° – 50° |
| December | 36° | 20° | 1.9" | 8.8" | 10 | 13° – 38° |
| Year | 60° | 41° | 37.2" | 36.1" | 117 |
Heating and cooling a home in Rock Island
85% of the work is heating, so the furnace matters far more than the air conditioner.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. Source: NOAA station normals.
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 13° to 38°. June is the most reliable, staying within 7°.
Common questions about Rock Island’s climate
What is the coldest month in Rock Island?
January, with a typical high of 31° and a low of 14°.
What is the hottest month in Rock Island?
July, with a typical high of 85° and a low of 65°. About 22 days a year reach 90°.
How much snow does Rock Island get?
About 36 inches in a normal winter, most of it in January.
When is the first frost in Rock Island?
In half of years the first 32° night comes by October 18, and the last spring frost by April 24.
What is the rainiest month in Rock Island?
June, with 4.9 inches of rain and melted snow. The year totals 37 inches.
Neighbors talk weather
Gardens, snow, and the best days of the year in Rock Island.
Your answer becomes a post in Town Square.
Temperatures and rainfall come from NOAA’s gridded climate normals for Rock Island itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Moline Quad City Intl Airport, IL (3 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000. Today’s forecast: National Weather Service.