Frost dates for 17970Saint Clair, PA
The average last spring frost in Saint Clair is April 16 and the average first fall frost is October 25, giving a typical growing season of about 189 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 16
- Average first fall frost
- Oct 25
- Growing season
- 189 days
Safer after May 3 (1-in-10 risk)
Possible by Oct 9 (1-in-10 risk)
Last frost typically in 164 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Apr 16 · Apr 30 · May 16 | Oct 1 · Oct 13 · Oct 30 | 165 days | 100% |
| Frost / freeze (32°F) | Apr 2 · Apr 16 · May 3 | Oct 9 · Oct 25 · Nov 7 | 189 days | 100% |
| Hard freeze (28°F) | Mar 20 · Apr 3 · Apr 17 | Oct 18 · Nov 3 · Nov 17 | 214 days | 100% |
Planting calendar for Saint Clair
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Mar 16 – May 22 |
| Tomatoes | Transplant outdoors | May 2 – Jul 5 |
| Peppers | Start seeds indoors | Mar 16 – Apr 16 |
| Peppers | Transplant outdoors | May 16 – Jun 16 |
| Eggplant | Start seeds indoors | Apr 2 – May 1 |
| Eggplant | Transplant outdoors | May 16 – Jun 16 |
| Cucumbers | Sow outdoors | May 16 – Jul 15 |
| Summer squash | Sow outdoors | May 2 – Jun 16 |
| Winter squash & pumpkins | Sow outdoors | May 16 – Jun 16 |
| Snap beans | Sow outdoors | May 2 – Aug 7 |
| Sweet corn | Sow outdoors | May 2 – Jul 5 |
| Watermelon & cantaloupe | Sow outdoors | May 16 – Jun 16 |
| Okra | Sow outdoors | May 9 – Jun 1 |
| Peas | Sow outdoors (spring) | Mar 16 – May 1 |
| Potatoes | Plant outdoors (spring) | Mar 16 – May 16 |
| Onions | Start seeds indoors (spring) | Feb 2 – Mar 1 |
| Onions | Transplant outdoors (spring) | Apr 2 – May 1 |
| Broccoli | Start seeds indoors (spring) | Feb 26 – Apr 1 |
| Broccoli | Transplant outdoors (spring) | Apr 2 – May 1 |
| Broccoli | Start seeds indoors (fall) | Jun 25 – Jul 5 |
| Broccoli | Transplant outdoors (fall) | Jul 25 – Aug 5 |
| Cabbage | Start seeds indoors (spring) | Feb 16 – Mar 16 |
| Cabbage | Transplant outdoors (spring) | Mar 16 – Apr 16 |
| Cabbage | Start seeds indoors (fall) | Jun 15 – Jul 15 |
| Cabbage | Transplant outdoors (fall) | Jul 15 – Aug 15 |
| Leaf lettuce | Sow outdoors (spring) | Mar 16 – Jun 1 |
| Leaf lettuce | Sow outdoors (fall) | Jul 15 – Aug 31 |
| Spinach | Sow outdoors (spring) | Mar 9 – Apr 22 |
| Spinach | Sow outdoors (fall) | Aug 1 – Sep 5 |
| Radishes | Sow outdoors (spring) | Mar 16 – May 6 |
| Radishes | Sow outdoors (fall) | Jul 15 – Sep 15 |
| Kale | Sow outdoors (spring) | Apr 2 – Apr 22 |
| Kale | Sow outdoors (fall) | Jul 8 – Aug 15 |
| Carrots | Sow outdoors (spring) | Apr 16 – Jun 1 |
| Carrots | Sow outdoors (fall) | Jun 15 – Jul 31 |
| Garlic | Plant outdoors (fall) | Oct 15 – Nov 15 |
Where these dates come from
ZIP code 17970 is matched to the NOAA station Hamburg, PA, 25.2 km away, at 369 ft elevation (369 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Hamburg, PA (used) | 369 ft | Apr 16 | Oct 25 |
| Mahanoy City 2 N, PA | 1,710 ft | Apr 30 | Oct 22 |
| Bear Gap, PA | 1,015 ft | Apr 27 | Oct 20 |
| Reading 4 Nnw, PA | 360 ft | Apr 10 | Oct 31 |
Frost dates near Saint Clair
- Port Carbon, PA 17965 · last Apr 16, first Oct 25
- Pottsville, PA 17901 · last Apr 16, first Oct 25
- Seltzer, PA 17974 · last Apr 27, first Oct 20
- Cumbola, PA 17930 · last Apr 16, first Oct 25
- Mar Lin, PA 17951 · last Apr 16, first Oct 25
- New Philadelphia, PA 17959 · last Apr 16, first Oct 25
- Minersville, PA 17954 · last Apr 16, first Oct 25
- Frackville, PA 17931 · last Apr 30, first Oct 22
Frequently asked questions
- When is the last frost in Saint Clair, PA?
- For ZIP code 17970, the average last spring frost (32°F) is April 16, based on NOAA 1991-2020 climate normals for the Hamburg, PA weather station. There is a 1-in-10 chance of a frost after May 3.
- When is the first frost in Saint Clair, PA?
- The average first fall frost (32°F) is October 25. There is a 1-in-10 chance of frost by October 9, so tender plants are at risk from that point on.
- How long is the growing season in 17970?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 189 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.