Mary's River Covered Bridge · Photo: Nyttend · Public domainChester’s winters are milder and less snowy than most of the U.S.
A typical July afternoon reaches 88°, a January night drops to 24°, and about 12 inches of snow falls in a normal winter.
A year in Chester at a glance
Each month’s typical high and low, and what it brings.
What stands out about Chester’s climate
Compared with towns across the U.S., with Chester’s place in Illinois beside it.
What a year in Chester feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 202 frost-free days a year
In half of years the last 32° night comes by April 8 and the first by October 30. Frost and day counts come from NOAA’s station at Kaskaskia Rvr Navigation Lock, IL, 8 miles from the town’s center, 160 ft lower.
The 2023 USDA map puts Chester’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 0°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 12 inches of snow a winter
Snow, measured at Chester, IL, is heaviest from January through February, about 4 inches a month. Precipitation (rain plus melted snow) adds up to 44 inches a year; May is the wettest month and February the driest. Rain or snow falls on about 101 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Chester
76% of the work is heating. Months averaging under 55° run from November through March.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Kaskaskia Rvr Navigation Lock, IL.
Living with Chester’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
202 frost-free days in zone 7a. The last frost comes by Apr 8 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 30.
Months with highs of 62–84° and lows of 40° or more: April, May, September and October. 2.4 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Chester from natural hazards, earthquakes are the largest share (28%); heat waves, cold waves, winter storms and ice storms together are 22%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Chester and similar climates
TownRatings has no climate map of the towns around Chester yet.
Climates most like Chester’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Chester, IL | 24° | 88° | 44" | 12" |
| Lake of the Woods, VA | 25° | 88° | 44" | 11" |
| Republic, MO | 23° | 88° | 45" | 14" |
| Hurricane, WV | 25° | 87° | 44" | 11" |
| Landover, MD | 26° | 88° | 45" | 16" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Chester averaged 1.0° warmer than the 1900s. The biggest change is in February (+1.9°).
A smaller shift than in 77% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Chester compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Chester’s place among Illinois’.
Chester weather by month
Highs, lows and precipitation from NOAA’s grid at Chester’s center; snow, wet days and snow on the ground from Chester, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 41° | 24° | 2.7" | 3.7" | 8 | 26° – 43° |
| February | 46° | 27° | 2.7" | 3.7" | 8 | 26° – 46° |
| March | 57° | 36° | 3.8" | 1.1" | 10 | 39° – 59° |
| April | 68° | 45° | 5.1" | 0.0" | 10 | 49° – 62° |
| May | 77° | 55° | 5.2" | 0.0" | 11 | 60° – 72° |
| June | 85° | 64° | 4.3" | 0.0" | 9 | 68° – 80° |
| July | 88° | 68° | 3.8" | 0.0" | 8 | 73° – 84° |
| August | 87° | 65° | 3.1" | 0.0" | 8 | 70° – 82° |
| September | 81° | 57° | 2.9" | 0.0" | 7 | 65° – 76° |
| October | 69° | 46° | 3.2" | 0.1" | 8 | 53° – 63° |
| November | 55° | 36° | 4.0" | 0.5" | 8 | 37° – 52° |
| December | 45° | 28° | 3.0" | 2.9" | 8 | 23° – 46° |
| Year | 67° | 46° | 43.7" | 12.0" | 101 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 23° to 46°. October is the most reliable, staying within 10°.
Where Chester’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Chester’s center.
- Snow: Chester, IL (NOAA station in town).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Kaskaskia Rvr Navigation Lock, IL, 8 miles from the town’s center, 160 ft lower; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Chester’s climate
What is the weather like in Chester?
A typical July afternoon reaches 88°, a January night drops to 24°, and about 12 inches of snow falls in a normal winter. Milder January nights than 59% of U.S. towns; hotter July afternoons than 69% of U.S. towns.
How cold does it get in Chester in winter?
January nights average 24°. About 99 nights a year reach 32° or below and 1 reach 0° or below. In the coldest January of the last 30 years the month averaged 26°.
How much snow does Chester get?
About 12 inches in a normal winter at Chester, IL, heaviest from January through February, about 4 inches a month.
How hot does it get in Chester?
July, with a typical high of 88° and a low of 68°. About 58 days a year reach 90° and 4 reach 100° (Kaskaskia Rvr Navigation Lock, IL).
When is the first and last frost in Chester?
In half of years the last spring frost (32°) comes by April 8 and the first fall frost by October 30, about 202 frost-free days, at Kaskaskia Rvr Navigation Lock, IL.
What growing zone is Chester in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 0°.
What is the best time of year to visit Chester?
By one simple rule (highs of 62–84° and lows of 40° or more), April, May, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Chester getting warmer?
Yes: 1991–2020 averaged 1.0° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 77% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Chester.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.