St. Clair Inn · Photo: Notorious4life · CC BY-SA 3.0Summers in St. Clair are cooler than in 78% of U.S. towns
The depth of winter brings overnight lows near 18°. Precipitation peaks in May and eases off in February. Its yearly precipitation falls short of 77% of U.S. towns. Plan time outside from May to September, when highs sit at 69–82°.
A year in St. Clair at a glance
Each month’s typical high and low, and what it brings.
What stands out about St. Clair’s climate
Compared with towns across the U.S., with St. Clair’s place in Michigan beside it.
What a year in St. Clair feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 196 frost-free days a year
In half of years the last 32° night comes by April 19 and the first by November 3. Frost and day counts come from NOAA’s station at Port Huron, MI, 11 miles from the town’s center, at about the same height.
The 2023 USDA map puts St. Clair’s center in zone 6a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −6°. 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 36 inches of snow a winter
Snow, measured at Port Huron, MI, is heaviest from January through February, about 11 inches a month. Precipitation (rain plus melted snow) adds up to 35 inches a year; May is the wettest month and February the driest. Rain or snow falls on about 140 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in St. Clair
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 Port Huron, MI.
Living with St. Clair’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
196 frost-free days in zone 6a. The last frost comes by Apr 19 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 3.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 1.2 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in St. Clair from natural hazards, river flooding is the largest share (56%); heat waves, cold waves, winter storms and ice storms together are 24%. Normals are averages; the hazards page covers the extremes.
Natural hazards →St. Clair and its neighbors
Every town next door is within a degree of St. Clair in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like St. Clair’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. Clair, MI | 18° | 82° | 35" | 36" |
| Lake Forest, IL | 17° | 82° | 37" | 34" |
| North Dansville, NY | 17° | 82° | 33" | 36" |
| Pleasant Prairie, WI | 16° | 82° | 35" | 36" |
| Kendallville, IN | 17° | 83° | 38" | 36" |
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. Clair averaged 1.7° warmer than the 1900s. The biggest change is in December (+2.9°).
A bigger shift than in 70% 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. Clair compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with St. Clair’s place among Michigan’s.
St. Clair weather by month
Highs, lows and precipitation from NOAA’s grid at St. Clair’s center; snow, wet days and snow on the ground from Port Huron, MI. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 31° | 18° | 2.5" | 11.1" | 14 | 17 | 15° – 34° |
| February | 34° | 19° | 2.1" | 11.4" | 10 | 16 | 12° – 36° |
| March | 43° | 27° | 2.4" | 4.6" | 11 | 7 | 26° – 47° |
| April | 56° | 37° | 3.2" | 0.4" | 13 | 0 | 41° – 52° |
| May | 69° | 48° | 3.6" | 0.0" | 13 | 0 | 50° – 64° |
| June | 78° | 58° | 3.4" | 0.0" | 11 | 0 | 63° – 73° |
| July | 82° | 63° | 3.3" | 0.0" | 10 | 0 | 67° – 77° |
| August | 80° | 62° | 3.1" | 0.0" | 10 | 0 | 66° – 75° |
| September | 74° | 54° | 3.2" | 0.0" | 10 | 0 | 58° – 68° |
| October | 61° | 44° | 3.0" | 0.0" | 13 | 0 | 49° – 59° |
| November | 47° | 34° | 2.7" | 1.3" | 12 | 1 | 34° – 47° |
| December | 36° | 25° | 2.4" | 6.7" | 13 | 9 | 20° – 41° |
| Year | 58° | 41° | 35.0" | 35.5" | 140 | 50 |
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°. August is the most reliable, staying within 9°.
Where St. Clair’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. Clair’s center.
- Snow: Port Huron, MI.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Port Huron, MI, 11 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. Clair’s climate
What is the weather like in St. Clair?
A typical July afternoon reaches 82°, a January night drops to 18°, and about 36 inches of snow falls in a normal winter. Colder January nights than 69% of U.S. towns; cooler July afternoons than 78% of U.S. towns.
How cold does it get in St. Clair in winter?
January nights average 18°. About 122 nights a year reach 32° or below and 3 reach 0° or below. In the coldest January of the last 30 years the month averaged 15°.
How much snow does St. Clair get?
About 36 inches in a normal winter at Port Huron, MI, heaviest from January through February, about 11 inches a month, with snow on the ground about 50 days a year.
How hot does it get in St. Clair?
July, with a typical high of 82° and a low of 63°. About 10 days a year reach 90° (Port Huron, MI).
When is the first and last frost in St. Clair?
In half of years the last spring frost (32°) comes by April 19 and the first fall frost by November 3, about 196 frost-free days, at Port Huron, MI.
What growing zone is St. Clair in?
Zone 6a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −6°.
What is the best time of year to visit St. Clair?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is St. Clair getting warmer?
Yes: 1991–2020 averaged 1.7° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 70% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in St. Clair.
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.