Frost dates for Mercer Island, WA
When the last spring frost and first fall frost usually come, and when to plant, from 30 years of NOAA weather records.
Last spring frost
March 13
typical year
Safe to plant
April 1
frost is over in 9 of 10 years
First fall frost
November 17
typical year
Growing season
247 days
frost-free, typical year
Frost watch this week
Tonight's and the next six nights' lows from the National Weather Service forecast for the station's location. Frost: 32°F or colder. Possible frost: 33–36°F, mostly in low spots on clear, still nights.
When to plant
Counted from this page's frost dates. Warm-season crops wait for the safe-to-plant date.
| Crop | Start indoors | Plant outside | Fall planting |
|---|---|---|---|
| Cool-season crops | |||
| Peas | – | Feb 13 – 27 | – |
| Spinach | – | Jan 30 – Feb 20 | Sep 22 – Oct 6 |
| Lettuce | – | Feb 13 – Mar 6 | Sep 22 – Oct 6 |
| Radishes | – | Feb 13 – Mar 27 | Oct 6 – 20 |
| Onions | – | Feb 13 – 27 | – |
| Potatoes | – | Feb 20 – Mar 6 | – |
| Carrots | – | Feb 20 – Mar 13 | Aug 25 – Sep 8 |
| Beets | – | Feb 13 – 27 | Sep 8 – 22 |
| Kale | Jan 2 – 16 | Feb 13 – 27 | Sep 8 – 22 |
| Broccoli | Jan 2 – 16 | Feb 27 – Mar 13 | Sep 8 – 22 |
| Cabbage | Dec 19 – Jan 2 | Feb 13 – 27 | Sep 8 – 22 |
| Garlic | – | – | Oct 6 – 27 |
| Warm-season crops | |||
| Tomatoes | Feb 4 – 18 | Apr 1 – 15 | – |
| Peppers | Jan 28 – Feb 11 | Apr 8 – 22 | – |
| Cucumbers | – | Apr 1 – 22 | – |
| Zucchini | – | Apr 1 – 29 | – |
| Pumpkins | – | Apr 1 – 22 | – |
| Green beans | – | Apr 1 – Sep 8 | – |
| Sweet corn | – | Apr 1 – 29 | – |
| Basil | Feb 25 – Mar 11 | Apr 8 – 15 | – |
Onions: from sets. Green beans: until 10 weeks before the first fall frost. Garlic: harvest next summer.
The year at a glance
Start indoors Plant outside Fall planting
The chance of frost, by date
| 1 year in 10 | Half of years | 9 years in 10 | |
|---|---|---|---|
| Spring frost after | April 1 | March 13 | February 20 |
| Fall frost before | November 1 | November 17 | December 6 |
Frost here means 32°F or colder. Read across: in 1 year in 10, spring frost carries on past the first date, which is why that date is the safe-to-plant date.
Hard freeze (28°F)
A hard freeze kills most garden plants, even hardy ones. The last one in spring usually comes around February 18 (March 10 in a late year), and the first one in fall around December 2.
Towns that use these dates
This is the nearest NOAA station with frost records for 2 towns.
Mercer Island, Beaux Arts Village
Where these dates come from
NOAA weather station SEATTLE BOEING FLD, WA US (USW00024234), 1991–2020 climate normals. It's the nearest station for 19 zip codes, all within 9 miles:
98040, 98101, 98104, 98106, 98108, 98116, 98118, 98121, 98122, 98126, 98134, 98136, 98144, 98146, 98154, 98164, 98168, 98174, 98353
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.