Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for Seattle, WA

Seattle, WA is in USDA zone 9a across its 59 ZIP codes. The median last spring frost is March 13 and the first fall frost November 17.

Seattle on the zone map

Outlined: its 38 ZIP code areas · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone9a20 to 25 °F

ZIP codes59

Last frostMar 13

First frostNov 17

Growing season247 days

9a 59 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Seattle, WA…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Seattle, WA

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMarch 13median — 50% chance of a later frost

Safe for tender plantsApril 1only 10% chance of frost after

First fall frostNovember 17median — 10% chance by Nov 1

Growing season247 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 18 and returns around December 2.

From the NOAA station Seattle Boeing Field, WA, elevation 20 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in Seattle

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Jan 30 – Feb 13

SpinachSow outdoors · Jan 30 – Feb 20

Broccoli, cabbageStart indoors · Jan 2 – Jan 16

Broccoli, cabbageTransplant · Feb 20 – Mar 6

Onion setsPlant outdoors · Feb 13 – Feb 27

PotatoesPlant outdoors · Feb 20 – Mar 6

LettuceSow outdoors · Feb 13 – Feb 27

Carrots, beetsSow outdoors · Feb 20 – Mar 6

TomatoesStart indoors · Jan 16 – Jan 30

TomatoesTransplant · Mar 20 – Apr 3

Peppers, eggplantStart indoors · Jan 2 – Jan 16

Peppers, eggplantTransplant · Mar 27 – Apr 10

BeansSow outdoors · Mar 20 – Apr 3

Sweet cornSow outdoors · Mar 20 – Apr 3

Cucumbers, squashSow outdoors · Mar 20 – Apr 3

Fall lettuce, spinachSow outdoors · Sep 22 – Oct 6

GarlicPlant cloves · Nov 3 – Dec 8

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 13) and first fall frost (Nov 17) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 98164 came on Feb 5 — 10 days earlier than the 1991–2020 average (Feb 15).

average
Feb 152026
Feb 5

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Soil in Seattle, WA

The soil mapped at the center of ZIP 98164 is Anthraltic Xerorthents — gravelly sandy loam, moderately well drained. Much of the area is built over (urban land); this is the natural soil underneath.

TextureGravelly sandy loamdrains and warms fast; dries out and needs more feeding

pH5.8moderately acidic; most vegetables like 6.0–7.0

DrainageModerately well drainednatural drainage class

Organic matter1%low — add compost

Hydrologic groupA/Ddrains fast once dried out; wet otherwise

Farmland classNot prime farmlandUSDA classification

Map unit: Urban land, 5 to 20 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 98164; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Seattle, WA

Summer high77 °Faverage high, July

Winter low36 °Faverage low, December

Hot days3days a year at 90 °F or more

Freezing nights30nights a year at 32 °F or less

Growing degree days2,392base 50 °F — the season’s usable heat

Longest day15 h 59 mindaylight on June 21

Shortest day8 h 25 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation38.5 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Seattle Boeing Field, WA (6 mi away); precipitation: Mercer Island 1.5 Nw, WA (4 mi away). Daylight is calculated from latitude.