What does USDA hardiness zone 6a mean in Oregon?

Zone 6a means an average annual extreme minimum winter temperature of −10 to −5 °F — the standard USDA measure of which perennials survive winter. 15 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 6a is the growing season longest?

Harper runs the longest season on this page at about 147 days; Burns is shortest at about 85 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 6a?

Using Juniper Canyon's frost dates (this page's median-season location): start seeds indoors about Apr 7 – Apr 21, then transplant outside about Jun 9 – Jun 16. 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 6a 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 15 locations listed (see the table above for each location's own dates).

USDA zone 6a in Oregon

−10 to −5 °F avg. annual extreme minimum · 15 locations in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 6a covers 15 locations across Oregon (average annual extreme minimum −10 to −5 °F): Beatty, OR, Beaver Marsh, OR, Burns, OR, Chiloquin, OR, Crane, OR, Crane, OR, and 9 more. Average last spring frost across this group ranges May 7 (Harper) to June 11 (Hines), and growing seasons run 85–147 days (Burns to Harper) — 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 Juniper Canyon, this group's median-season location.

USDA zone: 6a−10 to −5 °F
Last frost range: May 7–Jun 11avg, 32°F
First frost range: Sep 5–Oct 3avg, 32°F
Growing season range: 85–147days

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)
Beatty	—	Gerber Dam	May 31	Sep 21	114
Beaver Marsh	—	Lemolo Lake 3 Nnw	Jun 1	Sep 23	115
Burns	Hines	Burns Muni Ap	Jun 11	Sep 6	85
Chiloquin	Sprague River	Klamath Falls Intl Ap	Jun 9	Sep 18	99
Crane	—	Malheur Refuge Hq	May 29	Sep 18	113
Crane	Juntura	Riverside 7 Ssw	Jun 7	Sep 6	89
Haines	Unity	Baker City Muni Ap	May 25	Sep 15	111
Harper	Unity	Westfall	May 7	Oct 3	147
Hines	—	Squaw Butte-northern Great Bas	Jun 11	Sep 28	107
Juniper Canyon *	Prineville Lake Acres, Dayville	Barnes Stn	Jun 2	Sep 17	104
Juntura	—	Drewsey	Jun 5	Sep 5	91
Lostine	—	Wallowa	Jun 7	Sep 9	91
Silver Lake	—	Summer Lake 1 S	Jun 8	Sep 15	96
Three Rivers	Gilchrist	Wickiup Dam	Jun 7	Sep 18	100
Wallowa Lake	—	Joseph	May 24	Oct 1	126

* Juniper Canyon 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 (Juniper Canyon, representative)

Computed from Juniper Canyon's average frost dates — the median-season location in this Oregonzone 6a 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 Juniper Canyon (Oregon, zone 6a), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Apr 7 – Apr 21	Jun 9 – Jun 16	Aug 8 – Aug 28	—	matures comfortably
Pepper	Very tender	Mar 24 – Apr 7	Jun 16 – Jun 23	Aug 15 – Sep 14	—	matures, but with little margin
Cucumber	Tender	May 5 – May 12	Jun 9 – Jun 16	Jul 29 – Aug 18	—	matures comfortably
Summer squash / zucchini	Tender	—	Jun 9 – Jun 16	Jul 24 – Aug 8	—	matures comfortably
Bush bean	Tender	—	Jun 9 – Jun 16	Jul 29 – Aug 8	Jul 19 – Jul 29	matures comfortably
Sweet corn	Tender	—	Jun 2 – Jun 16	Aug 1 – Aug 31	—	matures comfortably
Basil	Very tender	Apr 21 – May 5	Jun 9 – Jun 16	Jul 9 – Jul 24	—	matures comfortably
Lettuce	Half-hardy	Apr 21 – May 5	May 5 – May 19	Jun 19 – Jul 4	Jul 5 – Jul 20	matures comfortably
Pea	Hardy	—	Apr 21 – May 5	Jun 15 – Jun 30	Jun 25 – Jul 10	matures comfortably
Spinach	Hardy	—	Apr 21 – May 5	May 31 – Jun 10	Jul 15 – Jul 25	matures comfortably
Carrot	Half-hardy	—	May 12 – May 19	Jul 11 – Jul 31	Jun 15 – Jul 5	matures comfortably
Broccoli	Half-hardy	Apr 7 – Apr 21	May 5 – May 19	Jun 29 – Jul 19	Jun 20 – Jul 10	matures comfortably

Which crops fit this growing season

Using Juniper Canyon's own 104-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 11 of 12 crops mature here with comfortable margin, 1matures with little room to spare. The tightest fits: pepper (+3 day 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 (Juniper Canyon)

From NOAA's 1991–2020 Climate Normals at station USC00350501. 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), Juniper Canyon.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	—	—	—	—	71
32°F (freeze)	Jun 2	Jun 25	Sep 17	Oct 1	104
28°F	May 12	Jun 1	Sep 30	Oct 16	140
24°F	Apr 28	May 14	Oct 13	Nov 2	170

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 15 locations is 1,846; Juniper Canyon's own reading is shown below.

Annual growing degree days for Juniper Canyon (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	2,108	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	4,174	cool-season crops (brassicas, greens)

Hardiness zone 6a in Oregon

Zone 6a means an average annual extreme minimum winter temperature of about −10 to −5 °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, 6b, 7a, 7b, 8a, 8b, 9a, 9b.

Explore zone 6a in other states at zone 6a, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 6a mean in Oregon?: Zone 6a means an average annual extreme minimum winter temperature of −10 to −5 °F — the standard USDA measure of which perennials survive winter. 15 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 6a is the growing season longest?: Harper runs the longest season on this page at about 147 days; Burns is shortest at about 85 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 6a?: Using Juniper Canyon's frost dates (this page's median-season location): start seeds indoors about Apr 7 – Apr 21, then transplant outside about Jun 9 – Jun 16. 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 6a 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 15 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.