Weather without surprises: St. Mary Township keeps close to the norm for U.S. towns
Peak summer warmth arrives in July, with afternoons near 86°. May is the wettest month here, with about 2.9 times the rain of January. By January nights alone, it runs colder than 72% of U.S. towns. Garden planting can start around April 13; autumn frost returns near October 22.
A year in St. Mary Township at a glance
Each month’s typical high and low, and what it brings.
What stands out about St. Mary Township’s climate
Compared with towns across the U.S., with St. Mary Township’s place in Illinois beside it.
What a year in St. Mary Township feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 191 frost-free days a year
In half of years the last 32° night comes by April 13 and the first by October 22. Frost and day counts come from NOAA’s station at Bentley, IL, 8 miles from the town’s center, at about the same height.
The 2023 USDA map puts St. Mary Township’s center in zone 6a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −8°. 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 24 inches of snow a winter
Snow, measured at Augusta, IL, falls mostly in January. Precipitation (rain plus melted snow) adds up to 40 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 St. Mary Township
83% of the work is heating. 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 Bentley, IL.
Living with St. Mary Township’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
191 frost-free days in zone 6a. The last frost comes by Apr 13 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 22.
Months with highs of 62–84° and lows of 40° or more: April, May, June, September and October.
Parks & trails →Cold waves are 22% of the yearly building losses FEMA expects in St. Mary Township from natural hazards, the largest share. Normals are averages; the hazards page covers the extremes.
Natural hazards →St. Mary Township and its neighbors
Every town next door is within a degree of St. Mary Township in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like St. Mary 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 |
|---|---|---|---|---|
| St. Mary Township, IL | 18° | 86° | 40" | 24" |
| Lock Haven, PA | 19° | 86° | 41" | 30" |
| Savannah, MO | 18° | 87° | 37" | 21" |
| Peru, IN | 19° | 84° | 40" | 21" |
| Dublin, OH | 21° | 85° | 40" | 24" |
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 St. Mary Township averaged 0.7° warmer than the 1900s. The biggest change is in December (+1.9°).
A smaller shift than in 92% 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 St. Mary Township compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with St. Mary Township’s place among Illinois’.
St. Mary Township weather by month
Highs, lows and precipitation from NOAA’s grid at St. Mary Township’s center; snow, wet days and snow on the ground from Augusta, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 34° | 18° | 1.7" | 7.5" | 8 | 14 | 19° – 38° |
| February | 39° | 22° | 1.9" | 6.1" | 7 | 8 | 18° – 41° |
| March | 51° | 31° | 2.5" | 3.1" | 10 | 3 | 33° – 55° |
| April | 64° | 41° | 4.0" | 1.0" | 11 | 0 | 44° – 59° |
| May | 74° | 53° | 5.1" | 0.0" | 12 | 0 | 57° – 72° |
| June | 83° | 62° | 5.0" | 0.0" | 10 | 0 | 69° – 76° |
| July | 86° | 66° | 4.1" | 0.0" | 8 | 0 | 71° – 81° |
| August | 85° | 63° | 3.9" | 0.0" | 8 | 0 | 68° – 79° |
| September | 78° | 55° | 3.7" | 0.0" | 7 | 0 | 61° – 72° |
| October | 66° | 44° | 3.2" | 0.1" | 9 | 0 | 49° – 60° |
| November | 51° | 33° | 2.6" | 1.1" | 8 | 1 | 34° – 51° |
| December | 39° | 23° | 2.0" | 5.2" | 8 | 9 | 16° – 40° |
| Year | 62° | 42° | 39.6" | 24.1" | 106 | 35 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 16° to 40°. June is the most reliable, staying within 7°.
Where St. Mary 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 St. Mary Township’s center.
- Snow: Augusta, IL.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Bentley, IL, 8 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 St. Mary Township’s climate
What is the weather like in St. Mary Township?
A typical July afternoon reaches 86°, a January night drops to 18°, and about 24 inches of snow falls in a normal winter. Colder January nights than 72% of U.S. towns; hotter July afternoons than 55% of U.S. towns.
How cold does it get in St. Mary Township in winter?
January nights average 18°. About 124 nights a year reach 32° or below and 7 reach 0° or below. In the coldest January of the last 30 years the month averaged 19°.
How much snow does St. Mary Township get?
About 24 inches in a normal winter at Augusta, IL, most of it in January, with snow on the ground about 35 days a year.
How hot does it get in St. Mary Township?
July, with a typical high of 86° and a low of 66°. About 31 days a year reach 90° and 1 reach 100° (Bentley, IL).
When is the first and last frost in St. Mary Township?
In half of years the last spring frost (32°) comes by April 13 and the first fall frost by October 22, about 191 frost-free days, at Bentley, IL.
What growing zone is St. Mary Township in?
Zone 6a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −8°.
What is the best time of year to visit St. Mary Township?
By one simple rule (highs of 62–84° and lows of 40° or more), April, May, June, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is St. Mary Township getting warmer?
Yes: 1991–2020 averaged 0.7° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 92% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in St. Mary 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.