Frost dates for 15664Mammoth, PA
The average last spring frost in Mammoth is April 18 and the average first fall frost is October 28, giving a typical growing season of about 193 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 18
- Average first fall frost
- Oct 28
- Growing season
- 193 days
Safer after May 6 (1-in-10 risk)
Possible by Oct 14 (1-in-10 risk)
Last frost typically in 166 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 29 · May 17 | Oct 4 · Oct 17 · Oct 29 | 169 days | 100% |
| Frost / freeze (32°F) | Apr 2 · Apr 18 · May 6 | Oct 14 · Oct 28 · Nov 10 | 193 days | 100% |
| Hard freeze (28°F) | Mar 23 · Apr 5 · Apr 21 | Oct 28 · Nov 8 · Nov 22 | 216 days | 100% |
Planting calendar for Mammoth
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 18 – May 24 |
| Tomatoes | Transplant outdoors | May 4 – Jul 8 |
| Peppers | Start seeds indoors | Mar 18 – Apr 18 |
| Peppers | Transplant outdoors | May 18 – Jun 18 |
| Eggplant | Start seeds indoors | Apr 4 – May 3 |
| Eggplant | Transplant outdoors | May 18 – Jun 18 |
| Cucumbers | Sow outdoors | May 18 – Jul 18 |
| Summer squash | Sow outdoors | May 4 – Jun 18 |
| Winter squash & pumpkins | Sow outdoors | May 18 – Jun 18 |
| Snap beans | Sow outdoors | May 4 – Aug 10 |
| Sweet corn | Sow outdoors | May 4 – Jul 8 |
| Watermelon & cantaloupe | Sow outdoors | May 18 – Jun 18 |
| Okra | Sow outdoors | May 11 – Jun 3 |
| Peas | Sow outdoors (spring) | Mar 18 – May 3 |
| Potatoes | Plant outdoors (spring) | Mar 18 – May 18 |
| Onions | Start seeds indoors (spring) | Feb 4 – Mar 3 |
| Onions | Transplant outdoors (spring) | Apr 4 – May 3 |
| Broccoli | Start seeds indoors (spring) | Feb 28 – Apr 3 |
| Broccoli | Transplant outdoors (spring) | Apr 4 – May 3 |
| Broccoli | Start seeds indoors (fall) | Jun 28 – Jul 8 |
| Broccoli | Transplant outdoors (fall) | Jul 28 – Aug 8 |
| Cabbage | Start seeds indoors (spring) | Feb 18 – Mar 18 |
| Cabbage | Transplant outdoors (spring) | Mar 18 – Apr 18 |
| Cabbage | Start seeds indoors (fall) | Jun 18 – Jul 18 |
| Cabbage | Transplant outdoors (fall) | Jul 18 – Aug 18 |
| Leaf lettuce | Sow outdoors (spring) | Mar 18 – Jun 3 |
| Leaf lettuce | Sow outdoors (fall) | Jul 18 – Sep 3 |
| Spinach | Sow outdoors (spring) | Mar 11 – Apr 24 |
| Spinach | Sow outdoors (fall) | Aug 4 – Sep 8 |
| Radishes | Sow outdoors (spring) | Mar 18 – May 8 |
| Radishes | Sow outdoors (fall) | Jul 18 – Sep 18 |
| Kale | Sow outdoors (spring) | Apr 4 – Apr 24 |
| Kale | Sow outdoors (fall) | Jul 11 – Aug 18 |
| Carrots | Sow outdoors (spring) | Apr 18 – Jun 3 |
| Carrots | Sow outdoors (fall) | Jun 18 – Aug 3 |
| Garlic | Plant outdoors (fall) | Oct 18 – Nov 18 |
Where these dates come from
ZIP code 15664 is matched to the NOAA station Pittsburgh Allegheny Co Ap, PA, 26.3 km away, at 1,248 ft elevation (2 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Pittsburgh Allegheny Co Ap, PA (used) | 1,248 ft | Apr 18 | Oct 28 |
| Murrysville 2 Sw, PA | 860 ft | Apr 22 | Oct 25 |
| Mt Pleasant, PA | 1,003 ft | May 1 | Oct 13 |
| Mckeesport, PA | 740 ft | May 2 | Oct 20 |
Frost dates near Mammoth
- Grapeville, PA 15634 · last Apr 29, first Oct 20
- Jeannette, PA 15644 · last May 2, first Oct 14
- Penn, PA 15675 · last May 2, first Oct 14
- Adamsburg, PA 15611 · last Apr 29, first Oct 20
- Manor, PA 15665 · last May 2, first Oct 20
- Westmoreland City, PA 15692 · last May 2, first Oct 14
- Arona, PA 15617 · last May 1, first Oct 13
- Wendel, PA 15691 · last Apr 29, first Oct 20
Frequently asked questions
- When is the last frost in Mammoth, PA?
- For ZIP code 15664, the average last spring frost (32°F) is April 18, based on NOAA 1991-2020 climate normals for the Pittsburgh Allegheny Co Ap, PA weather station. There is a 1-in-10 chance of a frost after May 6.
- When is the first frost in Mammoth, PA?
- The average first fall frost (32°F) is October 28. There is a 1-in-10 chance of frost by October 14, so tender plants are at risk from that point on.
- How long is the growing season in 15664?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 193 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.