St. Marys, PA climate
St. Marys has chilly, snowy winters and pleasant summers. A typical July afternoon reaches 80°, a January night drops to 16°, and about 53 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in St. Marys feels like
Winter
Spring
Summer
Fall
St. Marys 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 | 32° | 16° | 3.4" | 15.3" | 17 | 21 | 16° – 33° |
| February | 35° | 17° | 2.7" | 12.5" | 14 | 18 | 13° – 35° |
| March | 45° | 24° | 3.4" | 7.5" | 14 | 9 | 27° – 46° |
| April | 58° | 34° | 4.0" | 1.5" | 14 | 1 | 41° – 52° |
| May | 69° | 43° | 4.1" | 0 | 14 | 0 | 49° – 63° |
| June | 77° | 52° | 4.6" | 0 | 14 | 0 | 60° – 67° |
| July | 80° | 56° | 4.4" | 0 | 12 | 0 | 63° – 73° |
| August | 79° | 55° | 4.0" | 0 | 11 | 0 | 63° – 72° |
| September | 72° | 48° | 4.0" | 0 | 11 | 0 | 58° – 65° |
| October | 60° | 38° | 3.8" | 0.4" | 14 | 0 | 44° – 55° |
| November | 48° | 30° | 3.6" | 3.2" | 13 | 3 | 33° – 44° |
| December | 37° | 22° | 3.5" | 12.3" | 17 | 13 | 20° – 40° |
| Year | 58° | 36° | 45.5" | 52.7" | 166 | 65 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in St. Marys
St. Marys gets 45 inches of rain and melted snow a year. June is the wettest month and February the driest. Rain or snow falls on about 166 days a year. Snow covers the ground about 65 days of the year.
About 150 frost-free days a year
In half of years the last 32° night comes by May 13 and the first one by October 11. That leaves about 150 frost-free days for gardens, shorter than 81% of U.S. towns.
Heating and cooling a home in St. Marys
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In St. Marys, 94% of that work is heating and 6% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
St. Marys and its neighbors
St. Marys borders 5 towns with climate data. January nights across them vary by 1.3°. Jones has the coldest January nights (15°) and Shippen the hottest July afternoons (82°). St. Marys’s January low is 16° and its July high 80°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How St. Marys compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in St. Marys averaged 1.3° warmer than the 1900s. The biggest change is in December (+2.7°). The shift is larger than in 52% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at St. Marys’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. February swings the most: between 1991 and 2020 its average temperature ranged from 13° to 35°. June is the most reliable, staying within 7°.
Common questions about St. Marys’s climate
What is the coldest month in St. Marys?
January, with a typical high of 32° and a low of 16°.
What is the hottest month in St. Marys?
July, with a typical high of 80° and a low of 56°. About 3 days a year reach 90°.
How much snow does St. Marys get?
About 53 inches in a normal winter, most of it in January.
When is the first frost in St. Marys?
In half of years the first 32° night comes by October 11, and the last spring frost by May 13.
What is the rainiest month in St. Marys?
June, with 4.6 inches of rain and melted snow. The year totals 45 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for St. Marys itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Ridgway, PA (12 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.