Winter nights in Swan Township are colder than in 83% of U.S. towns
Expect July afternoons of about 85°. May is the wettest month here, with about 3.0 times the rain of January. It is a dry place: less rain and snow fall here than on 64% of U.S. towns. Keep the boiler serviced for the months from November to March, which average under 50°.
A year in Swan Township at a glance
Each month’s typical high and low, and what it brings.
What stands out about Swan Township’s climate
Compared with towns across the U.S., with Swan Township’s place in Illinois beside it.
What a year in Swan Township feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 177 frost-free days a year
In half of years the last 32° night comes by April 22 and the first by October 19. Frost and day counts come from NOAA’s station at Avon, IL, 9 miles from the town’s center, at about the same height.
The 2023 USDA map puts Swan Township’s center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −11°. 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 21 inches of snow a winter
Snow, measured at Prairie City 2s, IL, is heaviest from January through February, about 6 inches a month. Precipitation (rain plus melted snow) adds up to 39 inches a year; May is the wettest month and January the driest. Rain or snow falls on about 106 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Swan Township
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 Avon, IL.
Living with Swan Township’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
177 frost-free days in zone 5b. The last frost comes by Apr 22 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 19.
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 Swan Township from natural hazards, drought is the largest share (27%); heat waves, cold waves, winter storms and ice storms together are 27%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Swan Township and its neighbors
Every town next door is within a degree of Swan Township in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Swan 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 |
|---|---|---|---|---|
| Swan Township, IL | 15° | 85° | 39" | 21" |
| West Lafayette, IN | 18° | 84° | 40" | 19" |
| Osceola, IA | 13° | 85° | 37" | 28" |
| Defiance, OH | 19° | 85° | 37" | 24" |
| Savannah, MO | 18° | 87° | 37" | 21" |
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 Swan Township averaged 0.6° warmer than the 1900s. The biggest change is in December (+1.9°).
A smaller shift than in 95% 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 Swan Township compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Swan Township’s place among Illinois’.
Swan Township weather by month
Highs, lows and precipitation from NOAA’s grid at Swan Township’s center; snow, wet days and snow on the ground from Prairie City 2s, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 32° | 15° | 1.7" | 5.7" | 7 | 14 | 16° – 36° |
| February | 37° | 20° | 1.9" | 6.0" | 8 | 10 | 15° – 39° |
| March | 50° | 30° | 2.4" | 2.5" | 9 | 3 | 31° – 53° |
| April | 62° | 40° | 3.9" | 1.0" | 11 | 0 | 42° – 58° |
| May | 73° | 51° | 5.2" | 0.0" | 12 | 0 | 56° – 70° |
| June | 82° | 61° | 4.8" | 0.0" | 10 | 0 | 68° – 75° |
| July | 85° | 64° | 4.1" | 0.0" | 9 | 0 | 69° – 80° |
| August | 83° | 62° | 3.7" | 0.0" | 8 | 0 | 67° – 78° |
| September | 77° | 54° | 3.6" | 0.0" | 7 | 0 | 60° – 71° |
| October | 64° | 42° | 3.0" | 0.0" | 9 | 0 | 48° – 59° |
| November | 50° | 31° | 2.5" | 1.1" | 8 | 1 | 32° – 50° |
| December | 37° | 21° | 2.0" | 5.0" | 8 | 8 | 14° – 38° |
| Year | 61° | 41° | 38.8" | 21.3" | 106 | 36 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 15° to 39°. June is the most reliable, staying within 6°.
Where Swan 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 Swan Township’s center.
- Snow: Prairie City 2s, IL.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Avon, 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 Swan Township’s climate
What is the weather like in Swan Township?
A typical July afternoon reaches 85°, a January night drops to 15°, and about 21 inches of snow falls in a normal winter. Colder January nights than 83% of U.S. towns; cooler July afternoons than 52% of U.S. towns.
How cold does it get in Swan Township in winter?
January nights average 15°. About 144 nights a year reach 32° or below and 10 reach 0° or below. In the coldest January of the last 30 years the month averaged 16°.
How much snow does Swan Township get?
About 21 inches in a normal winter at Prairie City 2s, IL, heaviest from January through February, about 6 inches a month, with snow on the ground about 36 days a year.
How hot does it get in Swan Township?
July, with a typical high of 85° and a low of 64°. About 16 days a year reach 90° (Avon, IL).
When is the first and last frost in Swan Township?
In half of years the last spring frost (32°) comes by April 22 and the first fall frost by October 19, about 177 frost-free days, at Avon, IL.
What growing zone is Swan Township in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −11°.
What is the best time of year to visit Swan 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 Swan Township getting warmer?
Yes: 1991–2020 averaged 0.6° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 95% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Swan 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.