What does USDA hardiness zone 8a mean in Washington?

Zone 8a means an average annual extreme minimum winter temperature of 10 to 15 °F — the standard USDA measure of which perennials survive winter. 25 locations in Washington fall in this zone. It does not set planting dates; see the frost calendar below for that.

Where in Washington's zone 8a is the growing season longest?

Concrete runs the longest season on this page at about 229 days; Darrington is shortest at about 114 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.

When should I plant tomatoes in Washington's zone 8a?

Using Verlot's frost dates (this page's median-season location): start seeds indoors about Feb 18 – Mar 4, then transplant outside about Apr 22 – Apr 29. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.

Does every location in Washington's zone 8a have the same frost dates?

No — they do not all share a weather station, so frost dates vary by a week or more across the 25 locations listed (see the table above for each location's own dates).

USDA zone 8a in Washington

10 to 15 °F avg. annual extreme minimum · 25 locations in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 8a covers 25 locations across Washington (average annual extreme minimum 10 to 15 °F): Acme, WA, Ashford, WA, Baring, WA, Bellingham, WA, Chehalis, WA, Concrete, WA, and 19 more. Average last spring frost across this group ranges March 27 (Acme) to May 25 (Darrington), and growing seasons run 114–229 days (Darrington to Concrete) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Washington location's own frost dates; the printable planting calendar uses Verlot, this group's median-season location.

USDA zone: 8a10 to 15 °F
Last frost range: Mar 27–May 25avg, 32°F
First frost range: Sep 19–Nov 18avg, 32°F
Growing season range: 114–229days

Locations in this group

Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.

Own frost dates per location.
Location	Also covers	Nearest station	Last frost	First frost	Season (days)
Acme	—	Sedro-woolley	Mar 27	Nov 6	224
Ashford	Mineral, Elbe	Longmire Rainier Nps	May 22	Oct 3	134
Baring	Skykomish	Baring	Apr 14	Oct 29	197
Bellingham	—	Bellingham Intl Ap	Mar 31	Oct 30	211
Chehalis	Napavine, Winlock, Pe Ell, Ryderwood	Centralia	Apr 22	Oct 27	188
Concrete	—	Concrete Ppl Fish Stn	Mar 28	Nov 14	229
Cougar	—	Cougar 6 E	Apr 1	Nov 18	227
Dallesport	—	The Dalles Muni Ap	Apr 11	Oct 26	197
Darrington	—	Holden Village	May 25	Sep 19	114
Geneva	—	Bellingham 3 Ssw	Apr 1	Nov 2	216
Glacier	—	Upper Baker Dam	Apr 24	Oct 29	190
Greenwater	—	Mud Mtn Dam	Apr 18	Oct 31	196
Lynden	Peaceful Valley, Maple Falls, Everson, Nooksack	Clearbrook	Apr 18	Oct 18	185
Maryhill	—	Moro	May 12	Oct 4	143
McCleary	Oakville	Elma	May 1	Oct 14	169
Mossyrock	—	Mayfield Pwr Plt	Apr 7	Nov 13	215
Mossyrock	—	Longview	Apr 8	Nov 5	210
Onalaska	Toledo	Toledo Faa Ap	Apr 5	Oct 25	196
Packwood	—	Packwood	Apr 30	Oct 8	162
Pe Ell	—	Grays Rvr Hatchery	Apr 27	Oct 22	178
Riverpoint	—	Cedar Lake	Apr 23	Nov 1	193
Stevenson	—	Carson Fish Hatchery	May 2	Oct 9	161
Tumwater	Oakville	Olympia Ap	Apr 29	Oct 14	169
Verlot *	May Creek	Startup 1 E	Apr 15	Oct 25	192
Willapa	—	Raymond 2 S	Apr 26	Oct 17	177

* Verlot is this group's median-season location — the calendar below is computed from its data.

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.

Planting calendar (Verlot, representative)

Computed from Verlot's average frost dates — the median-season location in this Washingtonzone 8a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).

Crop

JanFebMarAprMayJunJulAugSepOctNovDec

Tomato

Pepper

Cucumber

Summer squash / zucchini

Start indoors
Plant out
Fall sowing
First harvest

Planting windows for Verlot (Washington, zone 8a), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Feb 18 – Mar 4	Apr 22 – Apr 29	Jun 21 – Jul 11	—	matures comfortably
Pepper	Very tender	Feb 4 – Feb 18	Apr 29 – May 6	Jun 28 – Jul 28	—	matures comfortably
Cucumber	Tender	Mar 18 – Mar 25	Apr 22 – Apr 29	Jun 11 – Jul 1	—	matures comfortably
Summer squash / zucchini	Tender	—	Apr 22 – Apr 29	Jun 6 – Jun 21	—	matures comfortably
Bush bean	Tender	—	Apr 22 – Apr 29	Jun 11 – Jun 21	Aug 26 – Sep 5	matures comfortably
Sweet corn	Tender	—	Apr 15 – Apr 29	Jun 14 – Jul 14	—	matures comfortably
Basil	Very tender	Mar 4 – Mar 18	Apr 22 – Apr 29	May 22 – Jun 6	—	matures comfortably
Lettuce	Half-hardy	Mar 4 – Mar 18	Mar 18 – Apr 1	May 2 – May 17	Aug 12 – Aug 27	matures comfortably
Pea	Hardy	—	Mar 4 – Mar 18	Apr 28 – May 13	Aug 2 – Aug 17	matures comfortably
Spinach	Hardy	—	Mar 4 – Mar 18	Apr 13 – Apr 23	Aug 22 – Sep 1	matures comfortably
Carrot	Half-hardy	—	Mar 25 – Apr 1	May 24 – Jun 13	Jul 23 – Aug 12	matures comfortably
Broccoli	Half-hardy	Feb 18 – Mar 4	Mar 18 – Apr 1	May 12 – Jun 1	Jul 28 – Aug 17	matures comfortably

Which crops fit this growing season

Using Verlot's own 192-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.

Frost & freeze dates (Verlot)

From NOAA's 1991–2020 Climate Normals at station USC00458034. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.

Freeze probabilities by temperature threshold (MM/DD, NOAA 1991–2020), Verlot.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	May 8	May 24	Oct 7	Oct 25	154
32°F (freeze)	Apr 15	May 7	Oct 25	Nov 15	192
28°F	Mar 18	Apr 11	Nov 12	Dec 12	240
24°F	Feb 19	Mar 16	Dec 3	Jan 14	294

Growing degree days

Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 25 locations is 1,803; Verlot's own reading is shown below.

Annual growing degree days for Verlot (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	1,904	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	4,466	cool-season crops (brassicas, greens)

Hardiness zone 8a in Washington

Zone 8a means an average annual extreme minimum winter temperature of about 10 to 15 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Washington spans 8 hardiness zones in this dataset — see all Washington locations for the full range, including zones6a, 6b, 7a, 7b, 8b, 9a, 9b.

Explore zone 8a in other states at zone 8a, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 8a mean in Washington?: Zone 8a means an average annual extreme minimum winter temperature of 10 to 15 °F — the standard USDA measure of which perennials survive winter. 25 locations in Washington fall in this zone. It does not set planting dates; see the frost calendar below for that.
Where in Washington's zone 8a is the growing season longest?: Concrete runs the longest season on this page at about 229 days; Darrington is shortest at about 114 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
When should I plant tomatoes in Washington's zone 8a?: Using Verlot's frost dates (this page's median-season location): start seeds indoors about Feb 18 – Mar 4, then transplant outside about Apr 22 – Apr 29. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
Does every location in Washington's zone 8a have the same frost dates?: No — they do not all share a weather station, so frost dates vary by a week or more across the 25 locations listed (see the table above for each location's own dates).

Sources & method

Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.