Frost dates for 98830Mansfield, WA
The average last spring frost in Mansfield is May 2 and the average first fall frost is October 12, giving a typical growing season of about 162 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 2
- Average first fall frost
- Oct 12
- Growing season
- 162 days
Safer after May 22 (1-in-10 risk)
Possible by Sep 27 (1-in-10 risk)
Last frost typically in 188 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 2 · May 23 · Jun 14 | Sep 13 · Oct 1 · Oct 14 | 128 days | 100% |
| Frost / freeze (32°F) | Apr 17 · May 2 · May 22 | Sep 27 · Oct 12 · Oct 29 | 162 days | 100% |
| Hard freeze (28°F) | Mar 26 · Apr 16 · May 5 | Oct 9 · Oct 25 · Nov 13 | 192 days | 100% |
Planting calendar for Mansfield
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 1 – Jun 7 |
| Tomatoes | Transplant outdoors | May 18 – Jun 22 |
| Peppers | Start seeds indoors | Apr 1 – May 2 |
| Peppers | Transplant outdoors | Jun 1 – Jul 2 |
| Eggplant | Start seeds indoors | Apr 18 – May 17 |
| Eggplant | Transplant outdoors | Jun 1 – Jul 2 |
| Cucumbers | Sow outdoors | Jun 1 – Jul 2 |
| Summer squash | Sow outdoors | May 18 – Jul 2 |
| Winter squash & pumpkins | Sow outdoors | Jun 1 – Jul 2 |
| Snap beans | Sow outdoors | May 18 – Jul 25 |
| Sweet corn | Sow outdoors | May 18 – Jun 22 |
| Watermelon & cantaloupe | Sow outdoors | Jun 1 – Jul 2 |
| Okra | Sow outdoors | May 25 – Jun 17 |
| Peas | Sow outdoors (spring) | Apr 1 – May 17 |
| Potatoes | Plant outdoors (spring) | Apr 1 – Jun 1 |
| Onions | Start seeds indoors (spring) | Feb 18 – Mar 17 |
| Onions | Transplant outdoors (spring) | Apr 18 – May 17 |
| Broccoli | Start seeds indoors (spring) | Mar 14 – Apr 17 |
| Broccoli | Transplant outdoors (spring) | Apr 18 – May 17 |
| Broccoli | Start seeds indoors (fall) | Jun 12 – Jun 22 |
| Broccoli | Transplant outdoors (fall) | Jul 12 – Jul 23 |
| Cabbage | Start seeds indoors (spring) | Mar 4 – Apr 1 |
| Cabbage | Transplant outdoors (spring) | Apr 1 – May 2 |
| Cabbage | Start seeds indoors (fall) | Jun 2 – Jul 2 |
| Cabbage | Transplant outdoors (fall) | Jul 2 – Aug 2 |
| Leaf lettuce | Sow outdoors (spring) | Apr 1 – Jun 17 |
| Leaf lettuce | Sow outdoors (fall) | Jul 2 – Aug 18 |
| Spinach | Sow outdoors (spring) | Mar 25 – May 8 |
| Spinach | Sow outdoors (fall) | Jul 19 – Aug 23 |
| Radishes | Sow outdoors (spring) | Apr 1 – May 22 |
| Radishes | Sow outdoors (fall) | Jul 2 – Sep 2 |
| Kale | Sow outdoors (spring) | Apr 18 – May 8 |
| Kale | Sow outdoors (fall) | Jun 25 – Aug 2 |
| Carrots | Sow outdoors (spring) | May 2 – Jun 17 |
| Carrots | Sow outdoors (fall) | Jun 2 – Jul 18 |
| Garlic | Plant outdoors (fall) | Oct 2 – Nov 2 |
Where these dates come from
ZIP code 98830 is matched to the NOAA station Hartline, WA, 32.5 km away, at 1,906 ft elevation (305 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Hartline, WA (used) | 1,906 ft | May 2 | Oct 12 |
| Chief Joseph Dam, WA | 834 ft | Apr 26 | Oct 11 |
| Coulee Dam 1 Sw, WA | 1,719 ft | Apr 22 | Oct 21 |
| Chelan, WA | 1,194 ft | Apr 17 | Oct 22 |
Frost dates near Mansfield
- Bridgeport, WA 98813 · last Apr 26, first Oct 11
- Electric City, WA 99123 · last Apr 22, first Oct 21
- Grand Coulee, WA 99133 · last Apr 22, first Oct 21
- Elmer City, WA 99124 · last Apr 22, first Oct 21
- Coulee City, WA 99115 · last May 2, first Oct 12
- Brewster, WA 98812 · last Apr 21, first Oct 15
- Coulee Dam, WA 99116 · last Apr 22, first Oct 21
- Nespelem, WA 99155 · last Apr 22, first Oct 21
Frequently asked questions
- When is the last frost in Mansfield, WA?
- For ZIP code 98830, the average last spring frost (32°F) is May 2, based on NOAA 1991-2020 climate normals for the Hartline, WA weather station. There is a 1-in-10 chance of a frost after May 22.
- When is the first frost in Mansfield, WA?
- The average first fall frost (32°F) is October 12. There is a 1-in-10 chance of frost by September 27, so tender plants are at risk from that point on.
- How long is the growing season in 98830?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 162 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.