Last frost date in Mercer Island, Washington
March 13
Average last frost in spring. In an early year (1 in 10) it's over by February 20; in a late year (1 in 10) it comes after April 1.
November 17
Average first frost in fall. 1 year in 10 it comes by November 1.
Source: NOAA U.S. Climate Normals 1991–2020, station Seattle Boeing Fld (USW00024234), 4 miles from Mercer Island, elevation 20 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Feb 20 | Mar 13 | Apr 1 |
| First frost in fall | Nov 1 | Nov 17 | Dec 6 |
Frost-free days in an average year: 247
| Chance in a year | Average last in spring | Average first in fall | |
|---|---|---|---|
| Light frost (36°F) | Every year | Apr 3 | Oct 31 |
| Frost (32°F) | Every year | Mar 13 | Nov 17 |
| Hard freeze (28°F) | 10 years in 10 | Feb 18 | Dec 2 |
Nights at 32°F or colder in an average year: 30
What to plant now in Mercer Island
- Collards plantsAug 25 – Nov 1Now
- BeetsSept 1 – Dec 1Now
- Cabbage plantsSept 1 – Dec 1Now
- CarrotsSept 1 – Nov 1Now
- DandelionSept 1 – Nov 1Now
- Head lettuce plantsSept 1 – Nov 1Now
- Leaf lettuceSept 1 – Nov 1Now
- LeeksSept 1 – Nov 1Now
- Mustard greensSept 1 – Dec 1Now
- Onion seedSept 1 – Nov 1Now
- ParsleySept 1 – Dec 31Now
- RadishesSept 1 – Dec 1Now
- TurnipsSept 1 – Nov 15Now
- Corn saladOct 1 – Dec 1Now
- Garden peasOct 1 – Dec 1Now
- Onion plants plantsOct 1 – Dec 31Now
- SpinachOct 1 – Dec 1Now
- Upland cressOct 1 – Dec 1Now
- Chervil and chivesNov 1 – Dec 31Soon
- Onion setsNov 1 – Dec 31Soon
- Spring planting calendar for an average last frost around March 10 Mercer Island: March 13
- Fall planting calendar for an average first frost around November 20 Mercer Island: November 17
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5. How we match the table.
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