When is the last frost in Seattle, WA?

The average last spring frost (50% probability of 32°F) in Seattle is around March 13, based on NOAA/NCEI 1991–2020 normals at the Seattle Boeing Fld, WA station (3.9 mi away). Half of years it falls outside that date, so wait 1–2 weeks past it before setting out frost-tender plants.

When is the first fall frost in Seattle?

The average first fall frost in Seattle, WA is around November 17, giving roughly a 247-day frost-free growing season.

What planting zone is Seattle, WA?

Seattle is in USDA plant hardiness zone 9a (average annual extreme minimum temperature 20 to 25°F), from the 2023 USDA Plant Hardiness Zone Map.

What is the weather like in Seattle?

In Seattle, WA the warmest month is August (avg high 77°F) and the coldest is February (avg low 37°F). It averages about 37.8″ of precipitation a year and 3.8″ of snow.

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Seattle, WA Planting Calendar & Frost Dates

USDA hardiness zone 9a · ZIP 98134 · elevation 18′ · NOAA & USDA data

Seattle is in USDA hardiness zone 9a (winters can dip to 20 to 25°F), with a growing season of about 247 days between the average last spring frost (March 13) and first fall frost (November 17). The warmest month is August (avg high 77°F); the coldest is February (avg low 37°F). It averages 37.8″ of precipitation a year and 3.8″ of snow, mostly mid-winter. Start cool-season crops several weeks before the last frost; wait until after it for tomatoes, peppers and other tender crops.

Hardiness zone

min temp 20 to 25°F

Last spring frost

March 13

avg (50% prob, 32°F)

First fall frost

November 17

avg (50% prob, 32°F)

Growing season

247 days

frost-free window

Warmest month

August

avg high 77°F

Month-by-month typical weather in Seattle

Average conditions from the NOAA/NCEI 1991–2020 U.S. Climate Normals at Seattle Sand Pt Wsfo, WA (8.3 mi away). Temperatures °F, precipitation & snow in inches.

Month	Avg high	Avg low	Mean	Precip (in)	Snow (in)
January	47.4	37.2	42.3	5.1	0.9
February	49.8	37	43.4	3.5	1
March	53.9	39.2	46.6	3.9	0
April	58.8	42.8	50.8	3	0
May	65.3	48.3	56.8	2.2	0
June	70.2	52.7	61.4	1.6	0
July	76.5	56.5	66.5	0.8	0
August	77	57.1	67.1	1	0
September	71.3	53.2	62.3	1.7	0
October	60.5	46.7	53.6	3.7	0
November	51.9	40.9	46.4	5.9	0.2
December	46.5	37	41.8	5.6	1.7

What to plant when in Seattle

Crop	Season	What to do & when
Tomatoes	warm	Start seeds indoors: January 30 · Transplant out: March 20
Peppers	warm	Start seeds indoors: January 16 · Transplant out: March 27
Cucumbers	warm	Direct sow: March 20
Zucchini / squash	warm	Direct sow: March 20
Bush beans	warm	Direct sow: March 20
Sweet corn	warm	Direct sow: March 20
Basil	warm	Transplant out: March 20
Peas	cool	Sow (spring): February 6 · Sow (fall): September 22
Spinach	cool	Sow (spring): January 30 · Sow (fall): September 22
Lettuce	cool	Sow (spring): February 13 · Sow (fall): September 22
Kale	cool	Transplant (spring): February 20 · Sow (fall): September 8
Broccoli	cool	Transplant (spring): February 27
Carrots	cool	Sow (spring): February 20 · Sow (fall): September 8
Onions	cool	Transplant (spring): February 13
Potatoes	cool	Plant seed potatoes: February 27
Radishes	cool	Sow (spring): February 13 · Sow (fall): October 6

Dates are computed from Seattle's average frost dates using standard cool-/warm-season timing. They're a starting point — a cold spring, a warm microclimate, or a fast-maturing variety can shift them by a week or two.

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Gear that helps you plant on time

Some links below are Amazon affiliate links (tag theboringthin-20). If you buy through them we may earn a small commission at no extra cost to you — it keeps this almanac free. We only list generic, genuinely-useful categories.

Soil thermometer →Know when the ground is warm enough to sow — the honest signal, not the calendar.Seed-starting trays + dome →Start tomatoes & peppers indoors on the schedule below.Seedling heat mat →Warms the soil for faster, more even germination indoors.Floating row cover / frost cloth →Buys you 4–8°F to beat an early or late frost.Raised garden bed kit →Warms and drains faster in spring than in-ground soil.Garden gloves →Basic kit for transplant day.

Nearby cities in Washington

Bellevue, WA Renton, WA Kirkland, WA Sammamish, WA Bremerton, WA Edmonds, WA Kent, WA Redmond, WA

Sources & method. Hardiness zone: 2023 USDA Plant Hardiness Zone Map (PRISM Climate Group, Oregon State University). Frost dates & growing season: NOAA/NCEI 1991–2020 U.S. Climate Normals, nearest station with published freeze normals — Seattle Boeing Fld, WA, 3.9 mi (confidence: high). Monthly weather normals: Seattle Sand Pt Wsfo, WA, 8.3 mi (confidence: high). ZIP centroid from U.S. Census 2023 ZCTA data. Frost dates are the 50%-probability date — half of years frost occurs outside the stated date. Nothing here is invented; where the nearest station is far, we say so. Last updated 2026-07-22.