Frost dates for 17055Mechanicsburg, PA
The average last spring frost in Mechanicsburg is April 15 and the average first fall frost is October 23, giving a typical growing season of about 189 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 15
- Average first fall frost
- Oct 23
- Growing season
- 189 days
Safer after May 2 (1-in-10 risk)
Possible by Oct 7 (1-in-10 risk)
Last frost typically in 163 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 14 · Apr 30 · May 15 | Sep 28 · Oct 12 · Oct 28 | 165 days | 100% |
| Frost / freeze (32°F) | Apr 1 · Apr 15 · May 2 | Oct 7 · Oct 23 · Nov 7 | 189 days | 100% |
| Hard freeze (28°F) | Mar 19 · Apr 3 · Apr 16 | Oct 20 · Nov 5 · Nov 21 | 214 days | 100% |
Planting calendar for Mechanicsburg
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 15 – May 21 |
| Tomatoes | Transplant outdoors | May 1 – Jul 3 |
| Peppers | Start seeds indoors | Mar 15 – Apr 15 |
| Peppers | Transplant outdoors | May 15 – Jun 15 |
| Eggplant | Start seeds indoors | Apr 1 – Apr 30 |
| Eggplant | Transplant outdoors | May 15 – Jun 15 |
| Cucumbers | Sow outdoors | May 15 – Jul 13 |
| Summer squash | Sow outdoors | May 1 – Jun 15 |
| Winter squash & pumpkins | Sow outdoors | May 15 – Jun 15 |
| Snap beans | Sow outdoors | May 1 – Aug 5 |
| Sweet corn | Sow outdoors | May 1 – Jul 3 |
| Watermelon & cantaloupe | Sow outdoors | May 15 – Jun 15 |
| Okra | Sow outdoors | May 8 – May 31 |
| Peas | Sow outdoors (spring) | Mar 15 – Apr 30 |
| Potatoes | Plant outdoors (spring) | Mar 15 – May 15 |
| Onions | Start seeds indoors (spring) | Feb 1 – Feb 28 |
| Onions | Transplant outdoors (spring) | Apr 1 – Apr 30 |
| Broccoli | Start seeds indoors (spring) | Feb 25 – Mar 31 |
| Broccoli | Transplant outdoors (spring) | Apr 1 – Apr 30 |
| Broccoli | Start seeds indoors (fall) | Jun 23 – Jul 3 |
| Broccoli | Transplant outdoors (fall) | Jul 23 – Aug 3 |
| Cabbage | Start seeds indoors (spring) | Feb 15 – Mar 15 |
| Cabbage | Transplant outdoors (spring) | Mar 15 – Apr 15 |
| Cabbage | Start seeds indoors (fall) | Jun 13 – Jul 13 |
| Cabbage | Transplant outdoors (fall) | Jul 13 – Aug 13 |
| Leaf lettuce | Sow outdoors (spring) | Mar 15 – May 31 |
| Leaf lettuce | Sow outdoors (fall) | Jul 13 – Aug 29 |
| Spinach | Sow outdoors (spring) | Mar 8 – Apr 21 |
| Spinach | Sow outdoors (fall) | Jul 30 – Sep 3 |
| Radishes | Sow outdoors (spring) | Mar 15 – May 5 |
| Radishes | Sow outdoors (fall) | Jul 13 – Sep 13 |
| Kale | Sow outdoors (spring) | Apr 1 – Apr 21 |
| Kale | Sow outdoors (fall) | Jul 6 – Aug 13 |
| Carrots | Sow outdoors (spring) | Apr 15 – May 31 |
| Carrots | Sow outdoors (fall) | Jun 13 – Jul 29 |
| Garlic | Plant outdoors (fall) | Oct 13 – Nov 13 |
Where these dates come from
ZIP code 17055 is matched to the NOAA station Harrisburg 1 Ne, PA, 16.1 km away, at 420 ft elevation (92 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Harrisburg 1 Ne, PA (used) | 420 ft | Apr 15 | Oct 23 |
| Harrisburg Cptl Cy Ap, PA | 340 ft | Apr 9 | Nov 1 |
| Carlisle Wtp, PA | 430 ft | Apr 23 | Oct 18 |
| Middletown Harrisburg Intl Ap, PA | 312 ft | Apr 9 | Nov 2 |
Frost dates near Mechanicsburg
- Grantham, PA 17027 · last Apr 15, first Oct 23
- Mechanicsburg, PA 17050 · last Apr 15, first Oct 23
- Camp Hill, PA 17001 · last Apr 15, first Oct 23
- New Kingstown, PA 17072 · last Apr 15, first Oct 23
- Dillsburg, PA 17019 · last Apr 15, first Oct 27
- Boiling Springs, PA 17007 · last Apr 23, first Oct 18
- Lemoyne, PA 17043 · last Apr 15, first Oct 23
- Franklintown, PA 17323 · last Apr 15, first Oct 27
Frequently asked questions
- When is the last frost in Mechanicsburg, PA?
- For ZIP code 17055, the average last spring frost (32°F) is April 15, based on NOAA 1991-2020 climate normals for the Harrisburg 1 Ne, PA weather station. There is a 1-in-10 chance of a frost after May 2.
- When is the first frost in Mechanicsburg, PA?
- The average first fall frost (32°F) is October 23. There is a 1-in-10 chance of frost by October 7, so tender plants are at risk from that point on.
- How long is the growing season in 17055?
- 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.