What does USDA hardiness zone 7b mean in Oregon?

Zone 7b means an average annual extreme minimum winter temperature of 5 to 10 °F — the standard USDA measure of which perennials survive winter. 10 locations in Oregon fall in this zone. It does not set planting dates; see the frost calendar below for that.

Where in Oregon's zone 7b is the growing season longest?

The Dalles runs the longest season on this page at about 191 days; Idanha is shortest at about 134 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 Oregon's zone 7b?

Using Hermiston's frost dates (this page's median-season location): start seeds indoors about Mar 1 – Mar 15, then transplant outside about May 3 – May 10. 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 Oregon's zone 7b 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 10 locations listed (see the table above for each location's own dates).

USDA zone 7b in Oregon

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

USDA plant hardiness zone 7b covers 10 locations across Oregon (average annual extreme minimum 5 to 10 °F): Black Butte Ranch, OR, Boardman, OR, Hermiston, OR, Hood River, OR, Idanha, OR, Ione, OR, and 4 more. Average last spring frost across this group ranges April 14 (Boardman) to May 27 (Rhododendron), and growing seasons run 134–191 days (Idanha to The Dalles) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Oregon location's own frost dates; the printable planting calendar uses Hermiston, this group's median-season location.

USDA zone: 7b5 to 10 °F
Last frost range: Apr 14–May 27avg, 32°F
First frost range: Sep 30–Oct 23avg, 32°F
Growing season range: 134–191days

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)
Black Butte Ranch	—	Belknap Springs 8 N	May 5	Oct 12	159
Boardman	Irrigon	Boardman	Apr 14	Oct 21	188
Hermiston *	Umatilla	Hermiston Muni Ap	Apr 26	Oct 10	167
Hood River	White Salmon, Mosier	Hood Rvr Exp Stn	Apr 20	Oct 13	177
Idanha	—	Marion Forks Fish Hatchery	May 15	Sep 30	134
Ione	—	Heppner	Apr 26	Oct 19	174
Odell	Parkdale	Parkdale 1 Nne	May 13	Oct 3	142
Rhododendron	—	Government Camp	May 27	Oct 9	134
The Dalles	Dufur	The Dalles	Apr 14	Oct 23	191
Wasco	—	Moro	May 12	Oct 4	143

* Hermiston 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 (Hermiston, representative)

Computed from Hermiston's average frost dates — the median-season location in this Oregonzone 7b 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 Hermiston (Oregon, zone 7b), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Mar 1 – Mar 15	May 3 – May 10	Jul 2 – Jul 22	—	matures comfortably
Pepper	Very tender	Feb 15 – Mar 1	May 10 – May 17	Jul 9 – Aug 8	—	matures comfortably
Cucumber	Tender	Mar 29 – Apr 5	May 3 – May 10	Jun 22 – Jul 12	—	matures comfortably
Summer squash / zucchini	Tender	—	May 3 – May 10	Jun 17 – Jul 2	—	matures comfortably
Bush bean	Tender	—	May 3 – May 10	Jun 22 – Jul 2	Aug 11 – Aug 21	matures comfortably
Sweet corn	Tender	—	Apr 26 – May 10	Jun 25 – Jul 25	—	matures comfortably
Basil	Very tender	Mar 15 – Mar 29	May 3 – May 10	Jun 2 – Jun 17	—	matures comfortably
Lettuce	Half-hardy	Mar 15 – Mar 29	Mar 29 – Apr 12	May 13 – May 28	Jul 28 – Aug 12	matures comfortably
Pea	Hardy	—	Mar 15 – Mar 29	May 9 – May 24	Jul 18 – Aug 2	matures comfortably
Spinach	Hardy	—	Mar 15 – Mar 29	Apr 24 – May 4	Aug 7 – Aug 17	matures comfortably
Carrot	Half-hardy	—	Apr 5 – Apr 12	Jun 4 – Jun 24	Jul 8 – Jul 28	matures comfortably
Broccoli	Half-hardy	Mar 1 – Mar 15	Mar 29 – Apr 12	May 23 – Jun 12	Jul 13 – Aug 2	matures comfortably

Which crops fit this growing season

Using Hermiston's own 167-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 (Hermiston)

From NOAA's 1991–2020 Climate Normals at station USW00004113. 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), Hermiston.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	May 8	May 22	Sep 28	Oct 12	142
32°F (freeze)	Apr 26	May 10	Oct 10	Oct 26	167
28°F	Apr 9	Apr 29	Oct 24	Nov 7	196
24°F	Mar 18	Apr 11	Nov 3	Nov 28	229

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 10 locations is 2,185; Hermiston's own reading is shown below.

Annual growing degree days for Hermiston (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	3,173	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	5,675	cool-season crops (brassicas, greens)

Hardiness zone 7b in Oregon

Zone 7b means an average annual extreme minimum winter temperature of about 5 to 10 °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. Oregon spans 9 hardiness zones in this dataset — see all Oregon locations for the full range, including zones5b, 6a, 6b, 7a, 8a, 8b, 9a, 9b.

Explore zone 7b in other states at zone 7b, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 7b mean in Oregon?: Zone 7b means an average annual extreme minimum winter temperature of 5 to 10 °F — the standard USDA measure of which perennials survive winter. 10 locations in Oregon fall in this zone. It does not set planting dates; see the frost calendar below for that.
Where in Oregon's zone 7b is the growing season longest?: The Dalles runs the longest season on this page at about 191 days; Idanha is shortest at about 134 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 Oregon's zone 7b?: Using Hermiston's frost dates (this page's median-season location): start seeds indoors about Mar 1 – Mar 15, then transplant outside about May 3 – May 10. 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 Oregon's zone 7b 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 10 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.