Frost dates for 17122Harrisburg, PA
The average last spring frost in Harrisburg is April 9 and the average first fall frost is November 1, giving a typical growing season of about 205 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 9
- Average first fall frost
- Nov 1
- Growing season
- 205 days
Safer after Apr 25 (1-in-10 risk)
Possible by Oct 16 (1-in-10 risk)
Last frost typically in 157 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 9 · Apr 22 · May 10 | Oct 7 · Oct 20 · Nov 3 | 180 days | 100% |
| Frost / freeze (32°F) | Mar 27 · Apr 9 · Apr 25 | Oct 16 · Nov 1 · Nov 15 | 205 days | 100% |
| Hard freeze (28°F) | Mar 13 · Mar 29 · Apr 9 | Oct 28 · Nov 12 · Dec 1 | 231 days | 100% |
Planting calendar for Harrisburg
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 9 – May 15 |
| Tomatoes | Transplant outdoors | Apr 25 – Jul 12 |
| Peppers | Start seeds indoors | Mar 9 – Apr 9 |
| Peppers | Transplant outdoors | May 9 – Jun 9 |
| Eggplant | Start seeds indoors | Mar 26 – Apr 24 |
| Eggplant | Transplant outdoors | May 9 – Jun 9 |
| Cucumbers | Sow outdoors | May 9 – Jul 22 |
| Summer squash | Sow outdoors | Apr 25 – Jun 9 |
| Winter squash & pumpkins | Sow outdoors | May 9 – Jun 9 |
| Snap beans | Sow outdoors | Apr 25 – Aug 14 |
| Sweet corn | Sow outdoors | Apr 25 – Jul 12 |
| Watermelon & cantaloupe | Sow outdoors | May 9 – Jun 9 |
| Okra | Sow outdoors | May 2 – May 25 |
| Peas | Sow outdoors (spring) | Mar 9 – Apr 24 |
| Potatoes | Plant outdoors (spring) | Mar 9 – May 9 |
| Onions | Start seeds indoors (spring) | Jan 26 – Feb 22 |
| Onions | Transplant outdoors (spring) | Mar 26 – Apr 24 |
| Broccoli | Start seeds indoors (spring) | Feb 19 – Mar 25 |
| Broccoli | Transplant outdoors (spring) | Mar 26 – Apr 24 |
| Broccoli | Start seeds indoors (fall) | Jul 2 – Jul 12 |
| Broccoli | Transplant outdoors (fall) | Aug 1 – Aug 12 |
| Cabbage | Start seeds indoors (spring) | Feb 9 – Mar 9 |
| Cabbage | Transplant outdoors (spring) | Mar 9 – Apr 9 |
| Cabbage | Start seeds indoors (fall) | Jun 22 – Jul 22 |
| Cabbage | Transplant outdoors (fall) | Jul 22 – Aug 22 |
| Leaf lettuce | Sow outdoors (spring) | Mar 9 – May 25 |
| Leaf lettuce | Sow outdoors (fall) | Jul 22 – Sep 7 |
| Spinach | Sow outdoors (spring) | Mar 2 – Apr 15 |
| Spinach | Sow outdoors (fall) | Aug 8 – Sep 12 |
| Radishes | Sow outdoors (spring) | Mar 9 – Apr 29 |
| Radishes | Sow outdoors (fall) | Jul 22 – Sep 22 |
| Kale | Sow outdoors (spring) | Mar 26 – Apr 15 |
| Kale | Sow outdoors (fall) | Jul 15 – Aug 22 |
| Carrots | Sow outdoors (spring) | Apr 9 – May 25 |
| Carrots | Sow outdoors (fall) | Jun 22 – Aug 7 |
| Garlic | Plant outdoors (fall) | Oct 22 – Nov 22 |
Where these dates come from
ZIP code 17122 is matched to the NOAA station Harrisburg Cptl Cy Ap, PA, 4 km away, at 340 ft elevation (25 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Harrisburg Cptl Cy Ap, PA (used) | 340 ft | Apr 9 | Nov 1 |
| Harrisburg 1 Ne, PA | 420 ft | Apr 15 | Oct 23 |
| Middletown Harrisburg Intl Ap, PA | 312 ft | Apr 9 | Nov 2 |
| Dehart Dam, PA | 537 ft | May 1 | Oct 16 |
Frost dates near Harrisburg
- Harrisburg, PA 17104 · last Apr 15, first Oct 23
- Lemoyne, PA 17043 · last Apr 15, first Oct 23
- New Cumberland, PA 17070 · last Apr 9, first Nov 1
- Camp Hill, PA 17012 · last Apr 15, first Oct 23
- Enola, PA 17025 · last Apr 15, first Oct 23
- Summerdale, PA 17093 · last Apr 15, first Oct 23
- Highspire, PA 17034 · last Apr 9, first Nov 2
- Lewisberry, PA 17339 · last Apr 9, first Nov 1
Frequently asked questions
- When is the last frost in Harrisburg, PA?
- For ZIP code 17122, the average last spring frost (32°F) is April 9, based on NOAA 1991-2020 climate normals for the Harrisburg Cptl Cy Ap, PA weather station. There is a 1-in-10 chance of a frost after April 25.
- When is the first frost in Harrisburg, PA?
- The average first fall frost (32°F) is November 1. There is a 1-in-10 chance of frost by October 16, so tender plants are at risk from that point on.
- How long is the growing season in 17122?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 205 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.