When should I plant tomatoes in ZIP 98101?

In ZIP 98101, the main tomatoes target is around Mar 27, based on the representative Seattle frost station and USDA zone 9a.

When should I start tomatoes seeds indoors in 98101?

Start tomatoes seeds indoors in ZIP 98101 around Feb 6, about 42 days before the Mar 20 last-frost estimate.

Is this a guaranteed planting date?

No. GrowZone uses frost-date estimates, hardiness zones, and crop timing rules for planning. Local microclimates and current weather can shift the right date.

ZIP 98101 planting calendar

When to plant tomatoes in Seattle, WA - Zone 9a

Q: When is the first frost in Seattle?

Seattle (ZIP 98101) has an average first fall frost around Nov 20, leaving about 245 frost-free days.

In ZIP 98101, plant tomatoes around Mar 27; this uses the Seattle frost station, USDA zone 9a, and tomatoes timing rules.

Your Seattle calendar has a 245-day estimated frost-free season. This estimate uses the representative Seattle frost station, USDA zone 9a, and tomatoes timing rules.

Source: seattle-tacoma frost station, USDA zone 9a, last updated 2026-06-28. Verify locally before planting high-value crops because microclimates, current weather, and yard exposure can move the safe date.

Reviewed by GrowZone Editorial. Calculated from the seattle-tacoma frost station and USDA zone 9a, last updated 2026-06-28.

In the Seattle area, gardeners usually wait until Mar 27 to set tomato transplants out because cold snaps near Mar 20 can still matter.

USDA zone 9a Seattle frost station Washington State University Extension Updated 2026-06-28

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Answer first

When to start tomatoes seeds indoors in Seattle

In ZIP 98101, start tomatoes seeds indoors around Feb 6, about 42 days before the Mar 20 last-frost estimate.

Start tomatoes seeds indoors in Seattle around Feb 6, about 42 days before the Mar 20 last-frost estimate.

Seed starting schedule

Tomatoes dates for Seattle, WA

Step	Date	How to use it
Start Indoors	February 6, 2026	Start seeds under lights or in a bright indoor seed-starting space.
Transplant Outdoors	March 27, 2026	Move hardened-off seedlings outside after the frost-risk window.

Last frost

When is the last frost in Seattle?

Seattle (ZIP 98101) has an average last spring frost around Mar 20.

First frost

When is the first frost in Seattle?

The average first fall frost is around Nov 20, giving about 245 frost-free days.

Season map

Tomatoes windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Start indoors

Feb 6

Transplant

Mar 27

Harvest

Jun 13

Frost watch

Sep 3

Reminder workflow

Every date has a next action

Start tomatoes indoorsFeb 6

Last frost windowMar 20

Transplant tomatoesMar 27

First tomatoes harvest windowJun 13

Last tomatoes sowing targetSep 3

Signal	Value	Why it matters
Last frost estimate	March 20, 2026	Warm-season transplant risk starts falling after this window.
First frost estimate	November 20, 2026	Fall planting counts backward from this date.
Season length	245 days	Longer seasons can support succession crops.
Spacing	18-24 in	Airflow and root space affect yield.
Soil temperature	60 F+	Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

Seattle frost history and USDA zone 9a shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

Washington State University Extension is the kind of local source to verify against when a crop is expensive, weather is unusual, or your yard has a cold pocket.

Crop note

Tomatoes timing notes

Harden seedlings off for a week before transplanting. Tomatoes prefers full sun, 18-24 in spacing, and soil near 60 F+.

For fall, count backward from Nov 20. A conservative last sowing target is around Sep 3.