Frost dates for 19318Chatham, PA
The average last spring frost in Chatham is April 19 and the average first fall frost is October 26, giving a typical growing season of about 189 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 19
- Average first fall frost
- Oct 26
- Growing season
- 189 days
Safer after May 3 (1-in-10 risk)
Possible by Oct 11 (1-in-10 risk)
Last frost typically in 167 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 17 · Apr 30 · May 14 | Oct 3 · Oct 13 · Oct 28 | 165 days | 100% |
| Frost / freeze (32°F) | Apr 1 · Apr 19 · May 3 | Oct 11 · Oct 26 · Nov 8 | 189 days | 100% |
| Hard freeze (28°F) | Mar 22 · Apr 5 · Apr 19 | Oct 21 · Nov 4 · Nov 21 | 214 days | 100% |
Planting calendar for Chatham
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 19 – May 25 |
| Tomatoes | Transplant outdoors | May 5 – Jul 6 |
| Peppers | Start seeds indoors | Mar 19 – Apr 19 |
| Peppers | Transplant outdoors | May 19 – Jun 19 |
| Eggplant | Start seeds indoors | Apr 5 – May 4 |
| Eggplant | Transplant outdoors | May 19 – Jun 19 |
| Cucumbers | Sow outdoors | May 19 – Jul 16 |
| Summer squash | Sow outdoors | May 5 – Jun 19 |
| Winter squash & pumpkins | Sow outdoors | May 19 – Jun 19 |
| Snap beans | Sow outdoors | May 5 – Aug 8 |
| Sweet corn | Sow outdoors | May 5 – Jul 6 |
| Watermelon & cantaloupe | Sow outdoors | May 19 – Jun 19 |
| Okra | Sow outdoors | May 12 – Jun 4 |
| Peas | Sow outdoors (spring) | Mar 19 – May 4 |
| Potatoes | Plant outdoors (spring) | Mar 19 – May 19 |
| Onions | Start seeds indoors (spring) | Feb 5 – Mar 4 |
| Onions | Transplant outdoors (spring) | Apr 5 – May 4 |
| Broccoli | Start seeds indoors (spring) | Mar 1 – Apr 4 |
| Broccoli | Transplant outdoors (spring) | Apr 5 – May 4 |
| Broccoli | Start seeds indoors (fall) | Jun 26 – Jul 6 |
| Broccoli | Transplant outdoors (fall) | Jul 26 – Aug 6 |
| Cabbage | Start seeds indoors (spring) | Feb 19 – Mar 19 |
| Cabbage | Transplant outdoors (spring) | Mar 19 – Apr 19 |
| Cabbage | Start seeds indoors (fall) | Jun 16 – Jul 16 |
| Cabbage | Transplant outdoors (fall) | Jul 16 – Aug 16 |
| Leaf lettuce | Sow outdoors (spring) | Mar 19 – Jun 4 |
| Leaf lettuce | Sow outdoors (fall) | Jul 16 – Sep 1 |
| Spinach | Sow outdoors (spring) | Mar 12 – Apr 25 |
| Spinach | Sow outdoors (fall) | Aug 2 – Sep 6 |
| Radishes | Sow outdoors (spring) | Mar 19 – May 9 |
| Radishes | Sow outdoors (fall) | Jul 16 – Sep 16 |
| Kale | Sow outdoors (spring) | Apr 5 – Apr 25 |
| Kale | Sow outdoors (fall) | Jul 9 – Aug 16 |
| Carrots | Sow outdoors (spring) | Apr 19 – Jun 4 |
| Carrots | Sow outdoors (fall) | Jun 16 – Aug 1 |
| Garlic | Plant outdoors (fall) | Oct 16 – Nov 16 |
Where these dates come from
ZIP code 19318 is matched to the NOAA station Avondale 2 N, PA, 2.3 km away, at 400 ft elevation (7 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Avondale 2 N, PA (used) | 400 ft | Apr 19 | Oct 26 |
| Coatesville 2 W, PA | 640 ft | Apr 19 | Oct 25 |
| W Chester 2 Nw, PA | 375 ft | Apr 26 | Oct 18 |
| Octoraro Lake, PA | 260 ft | Apr 26 | Oct 22 |
Frost dates near Chatham
- West Grove, PA 19390 · last Apr 19, first Oct 26
- Avondale, PA 19311 · last Apr 26, first Oct 18
- Toughkenamon, PA 19374 · last Apr 26, first Oct 18
- Kelton, PA 19346 · last Apr 19, first Oct 25
- Immaculata, PA 19345 · last Apr 26, first Oct 18
- Unionville, PA 19375 · last Apr 26, first Oct 18
- Kennett Square, PA 19348 · last Apr 26, first Oct 18
- Landenberg, PA 19350 · last Apr 7, first Nov 2
Frequently asked questions
- When is the last frost in Chatham, PA?
- For ZIP code 19318, the average last spring frost (32°F) is April 19, based on NOAA 1991-2020 climate normals for the Avondale 2 N, PA weather station. There is a 1-in-10 chance of a frost after May 3.
- When is the first frost in Chatham, PA?
- The average first fall frost (32°F) is October 26. There is a 1-in-10 chance of frost by October 11, so tender plants are at risk from that point on.
- How long is the growing season in 19318?
- 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.