Photo: Ben Jacobson (Kranar Drogin) · CC BY 2.5Midwinter lows in Forreston sink below those of 91% of U.S. towns
High summer brings afternoon highs near 83°. Summers stay cool: July afternoons here are cooler than in 68% of U.S. towns. Warming shows here too: 1.4° more than in 1901–2000, led by December. Long walks are most pleasant from May to October, when afternoons reach 62–83°.
A year in Forreston at a glance
Each month’s typical high and low, and what it brings.
What stands out about Forreston’s climate
Compared with towns across the U.S., with Forreston’s place in Illinois beside it.
What a year in Forreston feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 161 frost-free days a year
In half of years the last 32° night comes by April 29 and the first by October 7. Frost and day counts come from NOAA’s station at Polo 5nw, IL, 7 miles from the town’s center, at about the same height.
The 2023 USDA map puts Forreston’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −15°. 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 35 inches of snow a winter
Snow, measured at Freeport Waste Wtp, IL, falls mostly in January and December. Precipitation (rain plus melted snow) adds up to 39 inches a year; 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
Heating and cooling a home in Forreston
89% 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 Polo 5nw, IL.
Living with Forreston’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
161 frost-free days in zone 5b. The last frost comes by Apr 29 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 7.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October.
Parks & trails →Of the yearly building losses FEMA expects in Forreston from natural hazards, river flooding is the largest share (45%); heat waves, cold waves, winter storms and ice storms together are 14%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Forreston and its neighbors
Every town next door is within a degree of Forreston in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Forreston’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 |
|---|---|---|---|---|
| Forreston, IL | 12° | 83° | 39" | 35" |
| Grinnell, IA | 12° | 84° | 38" | 31" |
| Kendallville, IN | 17° | 83° | 38" | 36" |
| Sayre, PA | 17° | 84° | 37" | 35" |
| Ghent, 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 Forreston averaged 1.4° warmer than the 1900s. The biggest change is in December (+2.7°).
A bigger shift than in 56% 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 Forreston compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Forreston’s place among Illinois’.
Forreston weather by month
Highs, lows and precipitation from NOAA’s grid at Forreston’s center; snow, wet days and snow on the ground from Freeport Waste Wtp, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 29° | 12° | 1.6" | 9.7" | 9 | 20 | 11° – 33° |
| February | 34° | 17° | 1.8" | 8.5" | 8 | 15 | 12° – 36° |
| March | 46° | 27° | 2.5" | 3.8" | 9 | 5 | 29° – 52° |
| April | 60° | 37° | 3.8" | 0.8" | 11 | 1 | 39° – 55° |
| May | 71° | 49° | 4.4" | 0.0" | 13 | 0 | 54° – 66° |
| June | 80° | 58° | 5.3" | 0.0" | 12 | 0 | 66° – 74° |
| July | 83° | 62° | 4.3" | 0.0" | 10 | 0 | 67° – 79° |
| August | 81° | 60° | 4.1" | 0.0" | 10 | 0 | 65° – 77° |
| September | 75° | 52° | 3.7" | 0.0" | 9 | 0 | 57° – 68° |
| October | 62° | 40° | 2.9" | 0.2" | 9 | 0 | 47° – 58° |
| November | 47° | 29° | 2.4" | 2.6" | 8 | 2 | 30° – 47° |
| December | 34° | 19° | 1.9" | 8.9" | 9 | 12 | 12° – 37° |
| Year | 58° | 38° | 38.6" | 34.5" | 116 | 56 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 12° to 36°. June is the most reliable, staying within 8°.
Where Forreston’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 Forreston’s center.
- Snow: Freeport Waste Wtp, IL.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Polo 5nw, IL, 7 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 Forreston’s climate
What is the weather like in Forreston?
A typical July afternoon reaches 83°, a January night drops to 12°, and about 35 inches of snow falls in a normal winter. Colder January nights than 91% of U.S. towns; cooler July afternoons than 68% of U.S. towns.
How cold does it get in Forreston in winter?
January nights average 12°. About 138 nights a year reach 32° or below and 13 reach 0° or below. In the coldest January of the last 30 years the month averaged 11°.
How much snow does Forreston get?
About 35 inches in a normal winter at Freeport Waste Wtp, IL, most of it in January and December, with snow on the ground about 56 days a year.
How hot does it get in Forreston?
July, with a typical high of 83° and a low of 62°. About 17 days a year reach 90° (Polo 5nw, IL).
When is the first and last frost in Forreston?
In half of years the last spring frost (32°) comes by April 29 and the first fall frost by October 7, about 161 frost-free days, at Polo 5nw, IL.
What growing zone is Forreston in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −15°.
What is the best time of year to visit Forreston?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Forreston getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 56% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Forreston.
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.