Frost dates for 98145Seattle, 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 98145 is matched to the NOAA station Seattle Boeing Fld, WA, 8.8 km away, at 20 ft elevation (151 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 98111 · last Mar 13, first Nov 17
- Medina, WA 98039 · last Mar 8, first Nov 23
- Mercer Island, WA 98040 · last Mar 13, first Nov 17
- Bellevue, WA 98004 · last Mar 8, first Nov 23
- Kirkland, WA 98083 · last Mar 8, first Nov 23
- Seahurst, WA 98062 · last Mar 2, first Nov 23
- Renton, WA 98056 · last Mar 2, first Nov 23
- Bainbridge Island, WA 98110 · last Mar 29, first Nov 14
Frequently asked questions
- When is the last frost in Seattle, WA?
- For ZIP code 98145, 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 98145?
- 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.