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Will it freeze in St. Marys in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Sat, Nov 7: 32°F (Sat, Nov 7, 6:00 PM EST to Sun, Nov 8, 6:00 AM EST).
Tonight: forecast low 44°F. Above 36°F.
NWS forecast period: Thu, Nov 5, 6:00 PM EST to Fri, Nov 6, 6:00 AM EST.
5 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 44°F Above 36°F · Mostly Cloudy
- Fri, Nov 6 37°F Above 36°F · Chance Light Rain
- Sat, Nov 7 32°F Freeze · Light Rain Likely
- Sun, Nov 8 30°F Freeze · Slight Chance Rain Showers
- Mon, Nov 9 31°F Freeze · Mostly Clear
- Tue, Nov 10 30°F Freeze · Partly Cloudy
- Wed, Nov 11 26°F Hard freeze · Mostly Cloudy
Overnight lows from the National Weather Service forecast for this location. This covers the available forecast window, not the first freeze of the whole season. Frost can form above 32°F on clear, calm nights.
Frost and freeze probabilities
Freeze dates shift from year to year. Spring percentages describe the chance of a freeze after the stated date; fall percentages describe the chance of a freeze by that date. The 10% spring date is the cautious one: a later freeze happens about 1 year in 10.
These dates describe historical probabilities, not this year’s forecast or the earliest and latest possible freezes. Different weather stations or probability thresholds can produce different published dates for the same city.
Average first hard freeze in St. Marys
The median first fall hard-freeze date (28°F) is October 18, from NOAA’s 1991–2020 Climate Normals at Glen Hazel 2 NE Dam. This is the 50% probability date, not a forecast for this year.
| Temperature | Last spring date 90% · 50% · 10% chance of a later freeze | First fall date 10% · 50% · 90% chance of an earlier freeze | Season |
|---|---|---|---|
| 36°F frost possible | May 11 · May 27 · Jun 8 | Sep 12 · Sep 27 · Oct 8 | 121 days |
| 32°F freeze | Apr 28 · May 14 · May 29 | Sep 24 · Oct 6 · Oct 20 | 143 days |
| 28°F hard freeze | Apr 18 · May 3 · May 19 | Oct 2 · Oct 18 · Nov 3 | 168 days |
Average high temperature by month
1991–2020 normals at Glen Hazel 2 NE Dam
Average low temperature by month
Months with lows near or below freezing carry frost risk
Where these frost dates come from
The frost dates for St. Marys, PA come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Glen Hazel 2 NE Dam (station USC00363311, elevation 1,720 ft), 8.4 mi from St. Marys. Local conditions (valleys, hilltops, distance to water, city heat) can shift frost dates by days or weeks. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map (USDA ARS and Oregon State University PRISM). See our methodology.
Frost dates near St. Marys
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| DuBois, PA | 26 mi | May 6 | Oct 14 |
| Clearfield, PA | 30 mi | May 4 | Oct 11 |
| Bradford, PA | 35 mi | May 18 | Oct 4 |
| Warren, PA | 42 mi | May 4 | Oct 21 |
| Punxsutawney, PA | 42 mi | May 10 | Oct 12 |
| Olean, NY | 43 mi | May 7 | Oct 11 |
| Salamanca, NY | 50 mi | May 18 | Oct 1 |
| Bellefonte, PA | 54 mi | Apr 20 | Oct 26 |
| Tyrone, PA | 56 mi | May 13 | Oct 1 |
| State College, PA | 57 mi | Apr 20 | Oct 26 |
Frequently asked questions
When is the last frost in St. Marys?
On average, the last spring frost (32°F) in St. Marys is around May 14. In about 1 year in 10 it comes after May 29, and in 9 years in 10 it comes after April 28.
When is the first frost in St. Marys?
The first fall frost (32°F) usually arrives around October 6. There’s a 10% chance of a freeze by September 24 and a 90% chance by October 20.
Can it frost in St. Marys after the last frost date?
Yes. Frost can form on clear, calm nights even when the air stays above 32°F. Temperatures of 36°F or lower, cold enough for frost on exposed plants, have a 50% chance of occurring after May 27.
What growing zone is St. Marys?
St. Marys is in USDA Plant Hardiness Zone 5b (average annual extreme minimum temperature −15 to −10°F), based on the 2023 USDA map for ZIP code 15857. See growing zones in Pennsylvania.
More: all Pennsylvania frost dates · Pennsylvania growing zones · frost vs. freeze