Rock has cold, snowy winters and pleasant summers
A typical July afternoon reaches 83°, a January night drops to 12°, and about 35 inches of snow falls in a normal winter.
A year in Rock at a glance
Each month’s typical high and low, and what it brings.
What stands out about Rock’s climate
Read from where Rock sits among Illinois’s towns. The page puts what stands out first.
About 169 frost-free days a year
In half of years the last 32° night comes by April 26 and the first by October 13.
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 feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
35 inches of snow, 38 of rain and melt
June is the wettest month and January the driest. Rain or snow falls on about 116 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Living with Rock’s climate
What the numbers mean for a garden, a driveway, a furnace and a free afternoon.
169 frost-free days. The last frost comes by Apr 26 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 13.
About 35" a winter over 12 days with an inch or more, most in January. Snow covers the ground about 56 days a year.
Months averaging under 55° run from October through April. Heating is 91% of the year’s heating-and-cooling load.
About 11 days a year reach 90°, and July afternoons average 83°.
The nicest months are May, June, July, August and September.
Parks & trails →Normals are averages. Ice storms, nor’easters, floods and heat waves are on the natural hazards page.
Natural hazards →Warmer than it used to be
The last 30 years in Rock averaged 1.3° warmer than the 1900s. The biggest change is in December (+2.6°).
A bigger shift than in 57% of U.S. towns.
Change by month
How Rock compares
Against every U.S. town on TownTapestry, each counted once, with its place in Illinois.
Rock 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 | 28° | 12° | 1.6" | 9.7" | 9 | 20 | 10° – 33° |
| February | 33° | 16° | 1.6" | 8.5" | 8 | 15 | 12° – 36° |
| March | 45° | 26° | 2.3" | 3.8" | 9 | 5 | 27° – 51° |
| April | 59° | 37° | 3.7" | 0.8" | 11 | 1 | 39° – 55° |
| May | 71° | 48° | 4.2" | 0 | 13 | 0 | 54° – 66° |
| June | 80° | 58° | 5.6" | 0 | 12 | 0 | 66° – 74° |
| July | 83° | 62° | 4.2" | 0 | 10 | 0 | 66° – 80° |
| August | 81° | 60° | 4.2" | 0 | 10 | 0 | 65° – 76° |
| September | 75° | 52° | 3.7" | 0 | 9 | 0 | 57° – 68° |
| October | 62° | 40° | 3.0" | 0.2" | 9 | 0 | 47° – 57° |
| November | 46° | 29° | 2.4" | 2.6" | 8 | 2 | 29° – 47° |
| December | 33° | 19° | 2.0" | 8.9" | 9 | 12 | 12° – 37° |
| Year | 58° | 38° | 38.4" | 34.5" | 116 | 56 |
Heating and cooling a home in Rock
91% 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 12° to 37°. June is the most reliable, staying within 8°.
Common questions about Rock’s climate
What is the coldest month in Rock?
January, with a typical high of 28° and a low of 12°.
What is the hottest month in Rock?
July, with a typical high of 83° and a low of 62°. About 11 days a year reach 90°.
How much snow does Rock get?
About 35 inches in a normal winter, most of it in January.
When is the first frost in Rock?
In half of years the first 32° night comes by October 13, and the last spring frost by April 26.
What is the rainiest month in Rock?
June, with 5.6 inches of rain and melted snow. The year totals 38 inches.
Neighbors talk weather
Gardens, snow, and the best days of the year in Rock.
Your answer becomes a post in Town Square.
Temperatures and rainfall come from NOAA’s gridded climate normals for Rock itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Freeport Waste Wtp, IL (10 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.