Frost dates for 98144Seattle, WA
The average last spring frost in Seattle is March 13 and the average first fall frost is November 17, giving a typical growing season of about 247 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 13
- Average first fall frost
- Nov 17
- Growing season
- 247 days
Safer after Apr 1 (1-in-10 risk)
Possible by Nov 1 (1-in-10 risk)
First frost typically in 31 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) | Mar 17 · Apr 3 · Apr 28 | Oct 17 · Oct 31 · Nov 17 | 209 days | 100% |
| Frost / freeze (32°F) | Feb 20 · Mar 13 · Apr 1 | Nov 1 · Nov 17 · Dec 6 | 247 days | 100% |
| Hard freeze (28°F) | Jan 7 · Feb 18 · Mar 10 | Nov 12 · Dec 2 · Dec 30 | 295 days | 99% |
Planting calendar for Seattle
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 | Feb 10 – Apr 18 |
| Tomatoes | Transplant outdoors | Mar 29 – Jul 28 |
| Peppers | Start seeds indoors | Feb 10 – Mar 13 |
| Peppers | Transplant outdoors | Apr 12 – May 13 |
| Eggplant | Start seeds indoors | Feb 27 – Mar 28 |
| Eggplant | Transplant outdoors | Apr 12 – May 13 |
| Cucumbers | Sow outdoors | Apr 12 – Aug 7 |
| Summer squash | Sow outdoors | Mar 29 – May 13 |
| Winter squash & pumpkins | Sow outdoors | Apr 12 – May 13 |
| Snap beans | Sow outdoors | Mar 29 – Aug 30 |
| Sweet corn | Sow outdoors | Mar 29 – Jul 28 |
| Watermelon & cantaloupe | Sow outdoors | Apr 12 – May 13 |
| Okra | Sow outdoors | Apr 5 – Apr 28 |
| Peas | Sow outdoors (spring) | Feb 10 – Mar 28 |
| Potatoes | Plant outdoors (spring) | Feb 10 – Apr 12 |
| Onions | Start seeds indoors (spring) | Dec 30 – Jan 26 |
| Onions | Transplant outdoors (spring) | Feb 27 – Mar 28 |
| Broccoli | Start seeds indoors (spring) | Jan 23 – Feb 26 |
| Broccoli | Transplant outdoors (spring) | Feb 27 – Mar 28 |
| Broccoli | Start seeds indoors (fall) | Jul 18 – Jul 28 |
| Broccoli | Transplant outdoors (fall) | Aug 17 – Aug 28 |
| Cabbage | Start seeds indoors (spring) | Jan 13 – Feb 10 |
| Cabbage | Transplant outdoors (spring) | Feb 10 – Mar 13 |
| Cabbage | Start seeds indoors (fall) | Jul 8 – Aug 7 |
| Cabbage | Transplant outdoors (fall) | Aug 7 – Sep 7 |
| Leaf lettuce | Sow outdoors (spring) | Feb 10 – Apr 28 |
| Leaf lettuce | Sow outdoors (fall) | Aug 7 – Sep 23 |
| Spinach | Sow outdoors (spring) | Feb 3 – Mar 19 |
| Spinach | Sow outdoors (fall) | Aug 24 – Sep 28 |
| Radishes | Sow outdoors (spring) | Feb 10 – Apr 2 |
| Radishes | Sow outdoors (fall) | Aug 7 – Oct 8 |
| Kale | Sow outdoors (spring) | Feb 27 – Mar 19 |
| Kale | Sow outdoors (fall) | Jul 31 – Sep 7 |
| Carrots | Sow outdoors (spring) | Mar 13 – Apr 28 |
| Carrots | Sow outdoors (fall) | Jul 8 – Aug 23 |
| Garlic | Plant outdoors (fall) | Nov 7 – Dec 8 |
Where these dates come from
ZIP code 98144 is matched to the NOAA station Seattle Boeing Fld, WA, 6 km away, at 20 ft elevation (75 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Seattle Boeing Fld, WA (used) | 20 ft | Mar 13 | Nov 17 |
| Seattle Sand Pt Wsfo, WA | 60 ft | Mar 8 | Nov 23 |
| Renton Muni Ap, WA | 29 ft | Mar 13 | Nov 16 |
| Seattle Tacoma Intl Ap, WA | 370 ft | Mar 2 | Nov 23 |
Frost dates near Seattle
- Seattle, WA 98134 · last Mar 13, first Nov 17
- Mercer Island, WA 98040 · last Mar 13, first Nov 17
- Medina, WA 98039 · last Mar 8, first Nov 23
- Bellevue, WA 98004 · last Mar 8, first Nov 23
- Renton, WA 98056 · last Mar 2, first Nov 23
- Kirkland, WA 98083 · last Mar 8, first Nov 23
- Seahurst, WA 98062 · last Mar 2, first Nov 23
- Redmond, WA 98052 · last Mar 8, first Nov 23
Frequently asked questions
- When is the last frost in Seattle, WA?
- For ZIP code 98144, the average last spring frost (32°F) is March 13, based on NOAA 1991-2020 climate normals for the Seattle Boeing Fld, WA weather station. There is a 1-in-10 chance of a frost after April 1.
- When is the first frost in Seattle, WA?
- The average first fall frost (32°F) is November 17. There is a 1-in-10 chance of frost by November 1, so tender plants are at risk from that point on.
- How long is the growing season in 98144?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 247 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.