Frost dates for 98198Seattle, WA
The average last spring frost in Seattle is March 20 and the average first fall frost is November 10, giving a typical growing season of about 233 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 20
- Average first fall frost
- Nov 10
- Growing season
- 233 days
Safer after Apr 8 (1-in-10 risk)
Possible by Oct 26 (1-in-10 risk)
First frost typically in 9 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 26 · Apr 11 · Apr 30 | Oct 13 · Oct 27 · Nov 11 | 197 days | 100% |
| Frost / freeze (32°F) | Feb 27 · Mar 20 · Apr 8 | Oct 26 · Nov 10 · Nov 26 | 233 days | 100% |
| Hard freeze (28°F) | Jan 19 · Feb 25 · Mar 16 | Nov 6 · Nov 24 · Dec 20 | 275 days | 100% |
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 17 – Apr 25 |
| Tomatoes | Transplant outdoors | Apr 5 – Jul 21 |
| Peppers | Start seeds indoors | Feb 17 – Mar 20 |
| Peppers | Transplant outdoors | Apr 19 – May 20 |
| Eggplant | Start seeds indoors | Mar 6 – Apr 4 |
| Eggplant | Transplant outdoors | Apr 19 – May 20 |
| Cucumbers | Sow outdoors | Apr 19 – Jul 31 |
| Summer squash | Sow outdoors | Apr 5 – May 20 |
| Winter squash & pumpkins | Sow outdoors | Apr 19 – May 20 |
| Snap beans | Sow outdoors | Apr 5 – Aug 23 |
| Sweet corn | Sow outdoors | Apr 5 – Jul 21 |
| Watermelon & cantaloupe | Sow outdoors | Apr 19 – May 20 |
| Okra | Sow outdoors | Apr 12 – May 5 |
| Peas | Sow outdoors (spring) | Feb 17 – Apr 4 |
| Potatoes | Plant outdoors (spring) | Feb 17 – Apr 19 |
| Onions | Start seeds indoors (spring) | Jan 6 – Feb 2 |
| Onions | Transplant outdoors (spring) | Mar 6 – Apr 4 |
| Broccoli | Start seeds indoors (spring) | Jan 30 – Mar 5 |
| Broccoli | Transplant outdoors (spring) | Mar 6 – Apr 4 |
| Broccoli | Start seeds indoors (fall) | Jul 11 – Jul 21 |
| Broccoli | Transplant outdoors (fall) | Aug 10 – Aug 21 |
| Cabbage | Start seeds indoors (spring) | Jan 20 – Feb 17 |
| Cabbage | Transplant outdoors (spring) | Feb 17 – Mar 20 |
| Cabbage | Start seeds indoors (fall) | Jul 1 – Jul 31 |
| Cabbage | Transplant outdoors (fall) | Jul 31 – Aug 31 |
| Leaf lettuce | Sow outdoors (spring) | Feb 17 – May 5 |
| Leaf lettuce | Sow outdoors (fall) | Jul 31 – Sep 16 |
| Spinach | Sow outdoors (spring) | Feb 10 – Mar 26 |
| Spinach | Sow outdoors (fall) | Aug 17 – Sep 21 |
| Radishes | Sow outdoors (spring) | Feb 17 – Apr 9 |
| Radishes | Sow outdoors (fall) | Jul 31 – Oct 1 |
| Kale | Sow outdoors (spring) | Mar 6 – Mar 26 |
| Kale | Sow outdoors (fall) | Jul 24 – Aug 31 |
| Carrots | Sow outdoors (spring) | Mar 20 – May 5 |
| Carrots | Sow outdoors (fall) | Jul 1 – Aug 16 |
| Garlic | Plant outdoors (fall) | Oct 31 – Dec 1 |
Where these dates come from
ZIP code 98198 is matched to the NOAA station Kent, WA, 5.9 km away, at 30 ft elevation (62 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Kent, WA (used) | 30 ft | Mar 20 | Nov 10 |
| Seattle Tacoma Intl Ap, WA | 370 ft | Mar 2 | Nov 23 |
| Renton Muni Ap, WA | 29 ft | Mar 13 | Nov 16 |
| Seattle Boeing Fld, WA | 20 ft | Mar 13 | Nov 17 |
Frost dates near Seattle
- Kent, WA 98032 · last Mar 2, first Nov 23
- Seattle, WA 98148 · last Mar 2, first Nov 23
- Federal Way, WA 98063 · last Mar 2, first Nov 23
- Seahurst, WA 98062 · last Mar 2, first Nov 23
- Auburn, WA 98001 · last Mar 2, first Nov 23
- Burton, WA 98013 · last Mar 8, first Nov 14
- Renton, WA 98057 · last Mar 13, first Nov 16
- Vashon, WA 98070 · last Mar 2, first Nov 23
Frequently asked questions
- When is the last frost in Seattle, WA?
- For ZIP code 98198, the average last spring frost (32°F) is March 20, based on NOAA 1991-2020 climate normals for the Kent, WA weather station. There is a 1-in-10 chance of a frost after April 8.
- When is the first frost in Seattle, WA?
- The average first fall frost (32°F) is November 10. There is a 1-in-10 chance of frost by October 26, so tender plants are at risk from that point on.
- How long is the growing season in 98198?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 233 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.