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USDA hardiness zone lookup

Seattle (98101) — USDA Zone 9a

Seattle, Washington · 248-day growing season

Frost dates and growing season for 98101

USDA hardiness zoneZone 9a
Average last spring frostMarch 14
Average first fall frostNovember 17
Growing season length~248 days
Temperature range (F)20 to 30°F
Temperature range (C)-7 to -1°C

These are 50%-probability averages modeled from this ZIP's USDA hardiness zone and regional climate normals — not a single-station reading. In a typical year the last spring frost will have passed by March 14, but in a colder-than-average year it can run 1-2 weeks later. Plant tender crops (tomatoes, peppers, basil) once both soil and night temperatures are consistently warm — a thermometer beats the calendar.

Growing season in Seattle

Seattle, Washington sits in USDA Zone 9a, with roughly 248 frost-free days between an average last spring frost around March 14 and a first fall frost around November 17. That is a near year-round season — the limiting factor is summer heat, not frost, so schedule cool-season crops for winter and protect tender ones from extreme highs. Seattle lies near 47.6°N; higher-latitude gardens get longer midsummer days but a tighter shoulder season at this zone. As a large metro, the built-up core here typically runs up to half a zone warmer than outlying suburbs through the urban heat-island effect — sheltered city gardens often push tender crops a little earlier than the ZIP average suggests.

What grows in Seattle

Seattle falls in USDA Zone 9a, which means the same hardiness constraints apply as the full Zone 9 guide. Vegetables, herbs, and fruit trees rated to Zone 9a (or hardier) will overwinter here in a typical year.

What to plant in Seattle this week

Seattle is in the winter hold — outdoor planting is on pause. Use this time to plan, order seeds, and prep beds. Tomato and pepper seeds can start indoors 6-10 weeks before your last frost (March 14).

Full planting calendar for Seattle

Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 9 averages:

Local microclimate notes

Zone tables give you the average — but Seattlegardens vary. South-facing walls and paved areas can run a full half-zone warmer than the published rating. Low-lying spots, frost pockets, and shaded north sides can run colder. If you've gardened here a few seasons, your own frost record (the last time you actually got frost damage) is more accurate than any national average.

Source and methodology

Hardiness zone from the USDA Plant Hardiness Zone Map (2023 revision). Frost-date and growing-season figures are modeled from this ZIP's USDA hardiness zone and regional NOAA 1991-2020 climate normals — they are zone-level estimates, not a per-station record, so treat them as planning guidance and confirm against your own local frost history. Crop recommendations are drawn from US Cooperative Extension references and curated by the Growli editorial team. Last reviewed May 2026.

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