St. Marys weather by month
What a typical year looks like in St. Marys, Pennsylvania: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Ridgway, 20 km from St. Marys; records cover 1913–2026.
The year at a glance
- Precipitation a year
- 45.6 in1157 mm
- Snow a year
- 53 in134 cm
- Last spring freeze
- May 18
- First fall freeze
- Oct 3
- Heating degree days
- 6,731
- Cooling degree days
- 407
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are −7°−22° (heating, 99%) and 89°32° (cooling, 1%).
Month by month
St. Marys in January
Highs average 34°1° and lows 16°−9°, with 3.4 in87 mm of precipitation and 15 in39 cm of snow in a typical January.
- Record high
- 72°22° (1950)
- Record low
- −31°−35° (1984)
- Heating degree days
- 1241
- Cooling degree days
- 0
St. Marys in February
Highs average 37°3° and lows 17°−9°, with 2.7 in68 mm of precipitation and 13 in32 cm of snow in a typical February.
- Record high
- 74°23° (2017)
- Record low
- −35°−37° (1961)
- Heating degree days
- 1078
- Cooling degree days
- 0
St. Marys in March
Highs average 45°7° and lows 23°−5°, with 3.4 in87 mm of precipitation and 8 in19 cm of snow in a typical March.
- Record high
- 82°28° (1945)
- Record low
- −23°−31° (1916)
- Heating degree days
- 952
- Cooling degree days
- 0
St. Marys in April
Highs average 59°15° and lows 33°0°, with 3.9 in99 mm of precipitation and 1.5 in3.8 cm of snow in a typical April.
- Record high
- 92°33° (1927)
- Record low
- −1°−18° (1923)
- Heating degree days
- 574
- Cooling degree days
- 1
St. Marys in May
Highs average 70°21° and lows 43°6°, with 4.3 in110 mm of precipitation in a typical May.
- Record high
- 97°36° (1919)
- Record low
- 17°−8° (1947)
- Heating degree days
- 282
- Cooling degree days
- 25
St. Marys in June
Highs average 77°25° and lows 52°11°, with 4.6 in117 mm of precipitation in a typical June.
- Record high
- 106°41° (1927)
- Record low
- 27°−3° (1988)
- Heating degree days
- 81
- Cooling degree days
- 78
St. Marys in July
Highs average 81°27° and lows 57°14°, with 4.6 in116 mm of precipitation in a typical July.
- Record high
- 110°43° (1927)
- Record low
- 34°1° (1988)
- Heating degree days
- 24
- Cooling degree days
- 143
St. Marys in August
Highs average 80°27° and lows 55°13°, with 3.9 in99 mm of precipitation in a typical August.
- Record high
- 101°38° (1918)
- Record low
- 26°−3° (1982)
- Heating degree days
- 32
- Cooling degree days
- 116
St. Marys in September
Highs average 74°23° and lows 49°9°, with 4 in102 mm of precipitation in a typical September.
- Record high
- 103°39° (1927)
- Record low
- 22°−6° (1957)
- Heating degree days
- 154
- Cooling degree days
- 39
St. Marys in OctoberThis month
Highs average 62°16° and lows 38°3°, with 3.8 in96 mm of precipitation and 0.4 in1 cm of snow in a typical October.
- Record high
- 91°33° (1927)
- Record low
- 11°−12° (1952)
- Heating degree days
- 473
- Cooling degree days
- 5
St. Marys in November
Highs average 49°9° and lows 30°−1°, with 3.5 in89 mm of precipitation and 3 in8 cm of snow in a typical November.
- Record high
- 80°27° (1950)
- Record low
- −10°−23° (1930)
- Heating degree days
- 771
- Cooling degree days
- 0
St. Marys in December
Highs average 38°3° and lows 23°−5°, with 3.5 in88 mm of precipitation and 12 in31 cm of snow in a typical December.
- Record high
- 73°23° (1982)
- Record low
- −24°−31° (1960)
- Heating degree days
- 1069
- Cooling degree days
- 0