St
Clair has chilly winters and warm summers. A typical July afternoon reaches 84°, a January night drops to 20°, and about 26 inches of snow falls in a normal winter.
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
Read from where St. Clair sits among Pennsylvania’s towns. The page puts what stands out first.
26 inches of snow, 41 of rain and melt
September is the wettest month and February the driest. Rain or snow falls on about 136 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Living with St. Clair’s climate
What the numbers mean for a garden, a driveway, a furnace and a free afternoon.
194 frost-free days. 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 Oct 29.
About 26" a winter over 8 days with an inch or more, most in January. Snow covers the ground about 37 days a year.
Months averaging under 55° run from October through April. Heating is 87% of the year’s heating-and-cooling load.
About 11 days a year reach 90°, and July afternoons average 84°.
The nicest months are May, June, August, September and October.
Parks & trails →Normals are averages. Ice storms, nor’easters, floods and heat waves are on the natural hazards page.
Natural hazards →What a year in St. Clair feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 194 frost-free days a year
In half of years the last 32° night comes by April 19 and the first by October 29.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
St. Clair and its neighbors
Catharine has the coldest January nights next door (20°) and Catharine the hottest July afternoons (85°). Tap a town to see its climate.
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 1.1° warmer than the 1900s. The biggest change is in December (+2.2°).
A smaller shift than in 59% of U.S. towns.
Change by month
How St. Clair compares
Against every U.S. town on TownTapestry, each counted once, with its place in Pennsylvania.
St. Clair weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 36° | 20° | 2.7" | 7.5" | 11 | 13 | 20° – 37° |
| February | 40° | 22° | 2.4" | 6.8" | 10 | 12 | 19° – 39° |
| March | 49° | 28° | 3.3" | 4.8" | 11 | 5 | 33° – 50° |
| April | 62° | 38° | 3.6" | 0.2" | 13 | 0 | 45° – 56° |
| May | 72° | 48° | 3.9" | 0 | 14 | 0 | 54° – 67° |
| June | 80° | 57° | 3.9" | 0 | 12 | 0 | 64° – 71° |
| July | 84° | 61° | 3.8" | 0 | 11 | 0 | 68° – 77° |
| August | 83° | 59° | 3.8" | 0 | 11 | 0 | 67° – 75° |
| September | 76° | 52° | 4.0" | 0 | 10 | 0 | 61° – 68° |
| October | 64° | 41° | 3.3" | 0 | 11 | 0 | 48° – 58° |
| November | 51° | 32° | 3.1" | 1.3" | 10 | 1 | 36° – 47° |
| December | 41° | 25° | 3.1" | 5.1" | 11 | 7 | 24° – 42° |
| Year | 61° | 40° | 40.8" | 25.7" | 136 | 37 |
Heating and cooling a home in St. Clair
87% of the work is heating, so the furnace matters far more than the air conditioner.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. Source: NOAA station normals.
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 19° to 39°. June is the most reliable, staying within 7°.
Common questions about St. Clair’s climate
What is the coldest month in St. Clair?
January, with a typical high of 36° and a low of 20°.
What is the hottest month in St. Clair?
July, with a typical high of 84° and a low of 61°. About 11 days a year reach 90°.
How much snow does St. Clair get?
About 26 inches in a normal winter, most of it in January.
When is the first frost in St. Clair?
In half of years the first 32° night comes by October 29, and the last spring frost by April 19.
What is the rainiest month in St. Clair?
September, with 4.0 inches of rain and melted snow. The year totals 41 inches.
Neighbors talk weather
Gardens, snow, and the best days of the year in St. Clair.
Your answer becomes a post in Town Square.
Temperatures and rainfall come from NOAA’s gridded climate normals for St. Clair itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Williamsburg, PA (2 mi, snow) and Raystown Hq, PA (10 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000. Today’s forecast: National Weather Service.