Photo: Pubdog · Public domainJuly in St. Marys stays fresher than in 91% of U.S. towns
In January the night’s low is typically 16°. Expect the heaviest rain or snow in June and the lightest in February. Winter nights are cold: in January they are colder than in 81% of U.S. towns. Central heating does most of its work from October to April, in months below 50° on average.
A year in St. Marys at a glance
Each month’s typical high and low, and what it brings.
What stands out about St. Marys’ climate
Compared with towns across the U.S., with St. Marys’ place in Pennsylvania beside it.
What a year in St. Marys feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 143 frost-free days a year
In half of years the last 32° night comes by May 14 and the first by October 6. Frost and day counts come from NOAA’s station at Glen Hazel 2 Ne Dam, PA, 8 miles from the town’s center, 130 ft lower.
The 2023 USDA map puts St. Marys’ center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −11°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
About 53 inches of snow a winter
Snow, measured at Ridgway, PA, falls mostly in January. Precipitation (rain plus melted snow) adds up to 46 inches a year; June is the wettest month and February the driest. Rain or snow falls on about 166 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in St. Marys
97% 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 Glen Hazel 2 Ne Dam, PA.
Living with St. Marys’ climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
143 frost-free days in zone 5b. The last frost comes by May 14 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 6.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 99 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in St. Marys from natural hazards, river flooding is the largest share (68%); heat waves, cold waves, winter storms and ice storms together are 8%. Normals are averages; the hazards page covers the extremes.
Natural hazards →St. Marys and its neighbors
Shippen Township the hottest July afternoons (82°, 2° warmer). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like St. Marys’, 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. Marys, PA | 16° | 80° | 46" | 53" |
| Portsmouth, NH | 16° | 80° | 48" | 56" |
| Kittery, ME | 16° | 80° | 48" | 56" |
| Winchendon, MA | 13° | 81° | 47" | 51" |
| Sand Lake, NY | 15° | 82° | 43" | 53" |
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. Marys averaged 1.3° warmer than the 1900s. The biggest change is in December (+2.7°).
A smaller shift than in 58% 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. Marys compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with St. Marys’ place among Pennsylvania’s.
St. Marys weather by month
Highs, lows and precipitation from NOAA’s grid at St. Marys’ center; snow, wet days and snow on the ground from Ridgway, PA. 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" | 0.0" | 14 | 0 | 49° – 63° |
| June | 77° | 52° | 4.6" | 0.0" | 14 | 0 | 60° – 67° |
| July | 80° | 56° | 4.4" | 0.0" | 12 | 0 | 63° – 73° |
| August | 79° | 55° | 4.0" | 0.0" | 11 | 0 | 63° – 72° |
| September | 72° | 48° | 4.0" | 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 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 13° to 35°. June is the most reliable, staying within 7°.
Where St. Marys’ 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. Marys’ center.
- Snow: Ridgway, PA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Glen Hazel 2 Ne Dam, PA, 8 miles from the town’s center, 130 ft lower; 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. Marys’ climate
What is the weather like in St. Marys?
A typical July afternoon reaches 80°, a January night drops to 16°, and about 53 inches of snow falls in a normal winter. Colder January nights than 81% of U.S. towns; cooler July afternoons than 91% of U.S. towns.
How cold does it get in St. Marys in winter?
January nights average 16°. About 163 nights a year reach 32° or below and 12 reach 0° or below. In the coldest January of the last 30 years the month averaged 16°.
How much snow does St. Marys get?
About 53 inches in a normal winter at Ridgway, PA, most of it in January, with snow on the ground about 65 days a year.
How hot does it get in St. Marys?
July, with a typical high of 80°. 90° days are rare: none in a normal year at Glen Hazel 2 Ne Dam, PA.
When is the first and last frost in St. Marys?
In half of years the last spring frost (32°) comes by May 14 and the first fall frost by October 6, about 143 frost-free days, at Glen Hazel 2 Ne Dam, PA.
What growing zone is St. Marys in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −11°.
What is the best time of year to visit St. Marys?
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. Marys getting warmer?
Yes: 1991–2020 averaged 1.3° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 58% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in St. Marys.
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.