Cornwall Township has colder winter nights than 86% of U.S. towns
High summer brings afternoon highs near 84°. A year here swings 70° from midwinter lows to midsummer highs. Precipitation is light here, less than falls on 66% of U.S. towns. Garden planting can start around April 20; autumn frost returns near October 20.
A year in Cornwall Township at a glance
Each month’s typical high and low, and what it brings.
What stands out about Cornwall Township’s climate
Compared with towns across the U.S., with Cornwall Township’s place in Illinois beside it.
What a year in Cornwall Township feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 180 frost-free days a year
In half of years the last 32° night comes by April 20 and the first by October 20. Frost and day counts come from NOAA’s station at Geneseo, IL, 9 miles from the town’s center, at about the same height.
The 2023 USDA map puts Cornwall Township’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −12°. 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 28 inches of snow a winter
Snow, measured at Geneseo, IL, falls mostly in January. Precipitation (rain plus melted snow) adds up to 38 inches a year; May is the wettest month and January the driest. Rain or snow falls on about 108 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Cornwall Township
86% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Geneseo, IL.
Living with Cornwall Township’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
180 frost-free days in zone 5b. The last frost comes by Apr 20 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 20.
Months with highs of 62–84° and lows of 40° or more: May, June, August, September and October.
Parks & trails →Of the yearly building losses FEMA expects in Cornwall Township from natural hazards, river flooding is the largest share (33%); heat waves, cold waves, winter storms and ice storms together are 9%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Cornwall Township and its neighbors
Every town next door is within a degree of Cornwall Township in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Cornwall Township’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 |
|---|---|---|---|---|
| Cornwall Township, IL | 14° | 84° | 38" | 28" |
| Osceola, IA | 13° | 85° | 37" | 28" |
| Auburn, IN | 17° | 84° | 38" | 30" |
| Bryan, OH | 18° | 84° | 37" | 29" |
| Claverack, NY | 16° | 84° | 42" | 31" |
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 Cornwall Township averaged 1.0° warmer than the 1900s. The biggest change is in December (+2.2°).
A smaller shift than in 76% 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 Cornwall Township compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Cornwall Township’s place among Illinois’.
Cornwall Township weather by month
Highs, lows and precipitation from NOAA’s grid at Cornwall Township’s center; snow, wet days and snow on the ground from Geneseo, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 30° | 14° | 1.7" | 9.8" | 8 | 14° – 35° |
| February | 35° | 19° | 1.8" | 6.1" | 7 | 14° – 38° |
| March | 48° | 29° | 2.5" | 2.8" | 9 | 30° – 53° |
| April | 62° | 39° | 3.8" | 0.7" | 11 | 42° – 57° |
| May | 73° | 51° | 5.0" | 0.0" | 12 | 56° – 69° |
| June | 82° | 60° | 4.7" | 0.0" | 10 | 67° – 75° |
| July | 84° | 64° | 3.9" | 0.0" | 8 | 69° – 80° |
| August | 82° | 61° | 3.8" | 0.0" | 9 | 67° – 78° |
| September | 77° | 53° | 3.6" | 0.0" | 8 | 59° – 70° |
| October | 64° | 42° | 2.9" | 0.1" | 9 | 48° – 58° |
| November | 49° | 30° | 2.5" | 1.6" | 8 | 32° – 49° |
| December | 36° | 20° | 2.1" | 7.3" | 8 | 13° – 38° |
| Year | 60° | 40° | 38.4" | 28.4" | 108 |
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 8°.
Where Cornwall Township’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 Cornwall Township’s center.
- Snow: Geneseo, IL.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Geneseo, IL, 9 miles from the town’s center, at about the same height; 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 Cornwall Township’s climate
What is the weather like in Cornwall Township?
A typical July afternoon reaches 84°, a January night drops to 14°, and about 28 inches of snow falls in a normal winter. Colder January nights than 86% of U.S. towns; cooler July afternoons than 58% of U.S. towns.
How cold does it get in Cornwall Township in winter?
January nights average 14°. About 126 nights a year reach 32° or below and 9 reach 0° or below. In the coldest January of the last 30 years the month averaged 14°.
How much snow does Cornwall Township get?
About 28 inches in a normal winter at Geneseo, IL, most of it in January.
How hot does it get in Cornwall Township?
July, with a typical high of 84° and a low of 64°. About 22 days a year reach 90° (Geneseo, IL).
When is the first and last frost in Cornwall Township?
In half of years the last spring frost (32°) comes by April 20 and the first fall frost by October 20, about 180 frost-free days, at Geneseo, IL.
What growing zone is Cornwall Township in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −12°.
What is the best time of year to visit Cornwall Township?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Cornwall Township getting warmer?
Yes: 1991–2020 averaged 1.0° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 76% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Cornwall Township.
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.