Frost dates for 16137Mercer, PA
The average last spring frost in Mercer is May 15 and the average first fall frost is October 3, giving a typical growing season of about 140 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 15
- Average first fall frost
- Oct 3
- Growing season
- 140 days
Safer after Jun 1 (1-in-10 risk)
Possible by Sep 19 (1-in-10 risk)
Last frost typically in 193 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) | May 10 · May 27 · Jun 19 | Sep 4 · Sep 23 · Oct 6 | 118 days | 100% |
| Frost / freeze (32°F) | Apr 30 · May 15 · Jun 1 | Sep 19 · Oct 3 · Oct 19 | 140 days | 100% |
| Hard freeze (28°F) | Apr 19 · May 3 · May 21 | Sep 29 · Oct 13 · Nov 1 | 163 days | 100% |
Planting calendar for Mercer
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 | Apr 14 – Jun 20 |
| Tomatoes | Transplant outdoors | May 31 – Jun 13 |
| Peppers | Start seeds indoors | Apr 14 – May 15 |
| Peppers | Transplant outdoors | Jun 14 – Jul 15 |
| Eggplant | Start seeds indoors | May 1 – May 30 |
| Eggplant | Transplant outdoors | Jun 14 – Jul 15 |
| Cucumbers | Sow outdoors | Jun 14 – Jun 23 |
| Summer squash | Sow outdoors | May 31 – Jul 15 |
| Winter squash & pumpkins | Sow outdoors | Jun 14 – Jul 15 |
| Snap beans | Sow outdoors | May 31 – Jul 16 |
| Sweet corn | Sow outdoors | May 31 – Jun 13 |
| Watermelon & cantaloupe | Sow outdoors | Jun 14 – Jul 15 |
| Okra | Sow outdoors | Jun 7 – Jun 30 |
| Peas | Sow outdoors (spring) | Apr 14 – May 30 |
| Potatoes | Plant outdoors (spring) | Apr 14 – Jun 14 |
| Onions | Start seeds indoors (spring) | Mar 3 – Mar 30 |
| Onions | Transplant outdoors (spring) | May 1 – May 30 |
| Broccoli | Start seeds indoors (spring) | Mar 27 – Apr 30 |
| Broccoli | Transplant outdoors (spring) | May 1 – May 30 |
| Broccoli | Start seeds indoors (fall) | Jun 3 – Jun 13 |
| Broccoli | Transplant outdoors (fall) | Jul 3 – Jul 14 |
| Cabbage | Start seeds indoors (spring) | Mar 17 – Apr 14 |
| Cabbage | Transplant outdoors (spring) | Apr 14 – May 15 |
| Cabbage | Start seeds indoors (fall) | May 24 – Jun 23 |
| Cabbage | Transplant outdoors (fall) | Jun 23 – Jul 24 |
| Leaf lettuce | Sow outdoors (spring) | Apr 14 – Jun 30 |
| Leaf lettuce | Sow outdoors (fall) | Jun 23 – Aug 9 |
| Spinach | Sow outdoors (spring) | Apr 7 – May 21 |
| Spinach | Sow outdoors (fall) | Jul 10 – Aug 14 |
| Radishes | Sow outdoors (spring) | Apr 14 – Jun 4 |
| Radishes | Sow outdoors (fall) | Jun 23 – Aug 24 |
| Kale | Sow outdoors (spring) | May 1 – May 21 |
| Kale | Sow outdoors (fall) | Jun 16 – Jul 24 |
| Carrots | Sow outdoors (spring) | May 15 – Jun 30 |
| Carrots | Sow outdoors (fall) | May 24 – Jul 9 |
| Garlic | Plant outdoors (fall) | Sep 23 – Oct 24 |
Where these dates come from
ZIP code 16137 is matched to the NOAA station Mercer, PA, 0.9 km away, at 1,220 ft elevation (95 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Mercer, PA (used) | 1,220 ft | May 15 | Oct 3 |
| Slippery Rock 1 Ssw, PA | 1,260 ft | May 7 | Oct 14 |
| New Castle 1 N, PA | 825 ft | Apr 30 | Oct 23 |
| Jamestown 2 Nw, PA | 1,040 ft | May 4 | Oct 14 |
Frost dates near Mercer
- Fredonia, PA 16124 · last May 15, first Oct 3
- Jackson Center, PA 16133 · last May 15, first Oct 3
- New Wilmington, PA 16142 · last Apr 30, first Oct 23
- Grove City, PA 16127 · last May 7, first Oct 14
- Volant, PA 16156 · last May 7, first Oct 14
- Stoneboro, PA 16153 · last May 15, first Oct 3
- Clark, PA 16113 · last May 4, first Oct 14
- Hermitage, PA 16148 · last May 1, first Oct 17
Frequently asked questions
- When is the last frost in Mercer, PA?
- For ZIP code 16137, the average last spring frost (32°F) is May 15, based on NOAA 1991-2020 climate normals for the Mercer, PA weather station. There is a 1-in-10 chance of a frost after June 1.
- When is the first frost in Mercer, PA?
- The average first fall frost (32°F) is October 3. There is a 1-in-10 chance of frost by September 19, so tender plants are at risk from that point on.
- How long is the growing season in 16137?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 140 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.