St. Thomas, PA climate
St. Thomas has chilly, snowy winters and warm summers. A typical July afternoon reaches 86°, a January night drops to 22°, and about 31 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in St. Thomas feels like
Winter
Spring
Summer
Fall
St. Thomas 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 | 39° | 22° | 2.7" | 10.0" | 10 | 11 | 21° – 39° |
| February | 43° | 23° | 2.3" | 8.0" | 9 | 11 | 21° – 41° |
| March | 52° | 30° | 3.5" | 6.0" | 10 | 5 | 36° – 51° |
| April | 65° | 40° | 3.6" | 0.3" | 11 | 0 | 48° – 57° |
| May | 74° | 49° | 4.1" | 0 | 12 | 0 | 57° – 68° |
| June | 82° | 59° | 4.0" | 0 | 11 | 0 | 67° – 73° |
| July | 86° | 63° | 3.8" | 0 | 10 | 0 | 70° – 79° |
| August | 85° | 61° | 3.5" | 0 | 9 | 0 | 69° – 76° |
| September | 78° | 54° | 4.2" | 0 | 9 | 0 | 63° – 69° |
| October | 66° | 42° | 3.4" | 0 | 9 | 0 | 50° – 61° |
| November | 54° | 33° | 3.1" | 1.0" | 8 | 0 | 37° – 49° |
| December | 43° | 26° | 3.2" | 5.5" | 9 | 5 | 25° – 44° |
| Year | 64° | 42° | 41.5" | 30.8" | 117 | 31 |
“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. Thomas
St. Thomas gets 42 inches of rain and melted snow a year. September is the wettest month and February the driest. Rain or snow falls on about 117 days a year. Snow covers the ground about 31 days of the year.
About 188 frost-free days a year
In half of years the last 32° night comes by April 18 and the first one by October 25. That leaves about 188 frost-free days for gardens, longer than 62% of U.S. towns.
Heating and cooling a home in St. Thomas
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In St. Thomas, 85% of that work is heating and 15% 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. Thomas and its neighbors
St. Thomas borders 5 towns with climate data. January nights across them vary by 0.9°. Metal has the coldest January nights (21°) and Peters the hottest July afternoons (87°). St. Thomas’s January low is 22° and its July high 86°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How St. Thomas 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. Thomas averaged 1.6° warmer than the 1900s. The biggest change is in December (+2.6°). The shift is larger than in 73% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at St. Thomas’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 21° to 41°. September is the most reliable, staying within 7°.
Common questions about St. Thomas’s climate
What is the coldest month in St. Thomas?
January, with a typical high of 39° and a low of 22°.
What is the hottest month in St. Thomas?
July, with a typical high of 86° and a low of 63°. About 19 days a year reach 90°.
How much snow does St. Thomas get?
About 31 inches in a normal winter, most of it in January.
When is the first frost in St. Thomas?
In half of years the first 32° night comes by October 25, and the last spring frost by April 18.
What is the rainiest month in St. Thomas?
September, with 4.2 inches of rain and melted snow. The year totals 42 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for St. Thomas itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Chambersburg 1 Ese, PA (9 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.