What USDA hardiness zone is Umatilla County, Oregon?

Umatilla County, Oregon spans USDA hardiness zones 6b to 7b. 62% of its ZIP codes are zone 7a, so there is no single zone for the county.

When is the last spring frost in Umatilla County, Oregon?

The median last spring freeze runs March 25 – May 12 across the 7 NOAA weather stations serving Umatilla County, Oregon, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Oregon

Planting zones in Umatilla County, Oregon

This county spans USDA zones 6b to 7b, so there is no single zone for Umatilla County and anyone who gives you one is rounding. 62% of its ZIP codes are zone 7a; the rest are not.

USDA zones 6b–7b 3 zones across 13 ZIP codes

ZIP codes 13 13 have a NOAA station within range

Weather stations 7 NOAA 1991–2020 normals, across 3,215 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Umatilla County, Oregon as a whole. Hardiness zones and freeze dates are published per ZIP code, so yours is exact — enter it and this page will tell you your zone, which NOAA station it comes from and how far away that station is.

The growing season in Umatilla County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 27 – November 4 across the 7 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around January 28 – March 17 — counted back from a last spring freeze of March 25 – May 12 here.

Every spring date for your ZIP →

These are ranges across the whole county. The ZIP lookup above gives the dates from your own nearest station instead.

All 7 stations agreeAt least one station

Every one of the 7 NOAA stations serving this county counts May 12 – September 27 as growing season (138 days). Widening to any single station gives March 25 – November 4 (224 days).

That is a 86-day difference inside one county — which is why this page gives ranges rather than a single planting date. The ZIP lookup above resolves it to one station.

Which zone you are in depends where you are

Umatilla County covers 3 hardiness zones. A guide that gives the county one zone has picked whichever is largest and rounded everyone else into it — fine for the 62% in zone 7a and wrong for the other 38%. Here is the actual split.

Zone	ZIP codes	Share
7a	8	62%
6b	3	23%
7b	2	15%

Zones are published per ZIP code, so yours is exact even though the county's is not. The hardiness tool will tell you which one you are in.

Your freeze dates

Last spring freeze March 25 – May 12

First fall freeze September 27 – November 4

Across the 7 NOAA stations serving this county. These are medians — half of years freeze later than the date shown — so treat the later end of each range as the cautious one.

The growing season runs 135–218 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 85.1–88.6 °F in June–August. Summer rain over the same months runs 0.9–2.2" across those 6 stations, against the rough inch a week — about 13 inches over the same 92 days — that a vegetable garden is usually reckoned to want. The middle station covers about 15% of it, so a summer garden here is watered rather than rained on. The inches are NOAA's published normals; the inch a week is a rule of thumb, and it takes no account of a 87 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Umatilla County

Zones are published per ZIP code, not per county, so this is the exact answer rather than the county's average. The station column is the nearest one to that ZIP code's centroid and how far away it is — the same figure the tools use, shown here so you can see which ZIP codes are well covered and which are reaching.

ZIP code	USDA zone	Nearest NOAA station	Distance
97801	7a	Pendleton Dwtn, OR	2.1 km
97810	7a	Pendleton Branch Exp Stn, OR	18.7 km
97813	7a	Milton Freewater, OR	13.6 km
97826	7a	Hermiston Muni AP, OR	18.1 km
97835	7a	Pendleton Branch Exp Stn, OR	22.8 km
97838	7b	Hermiston 2 NW, OR	2.2 km
97859	6b	Pendleton Branch Exp Stn, OR	26.5 km
97862	7a	Milton Freewater, OR	7.5 km
97868	6b	Pilot Rock 1 SE, OR	7.7 km
97875	7a	Hermiston Muni AP, OR	8.8 km
97880	6b	Pilot Rock 1 SE, OR	43.3 km
97882	7b	Mcnary Dam #2, OR	4.9 km
97886	7a	Milton Freewater, OR	18.9 km

ZIP-code positions are area centroids, so a large rural ZIP code's listed distance is measured from the middle of its area rather than from any particular address in it.

When to start seeds in Umatilla County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 7 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	January 28 – March 17	8 wk before
🌶️ Peppers	Start indoors	January 28 – March 17	8 wk before
🥦 Broccoli	Start indoors	February 11 – March 31	6 wk before
🥬 Cabbage	Start indoors	February 11 – March 31	6 wk before
🥬 Collards	Start indoors	February 11 – March 31	6 wk before
🥬 Kale	Start indoors	February 11 – March 31	6 wk before
🥬 Leaf Lettuce	Start indoors	February 11 – March 31	6 wk before
🫛 Peas	Direct sow	February 11 – March 31	6 wk before
🥬 Spinach	Direct sow	February 11 – March 31	6 wk before
🍠 Sweet Potato	Start indoors	February 11 – March 31	6 wk before
🍅 Tomatoes	Start indoors	February 11 – March 31	6 wk before
🥬 Bok Choy	Start indoors	February 18 – April 7	5 wk before
🥬 Kohlrabi	Start indoors	February 18 – April 7	5 wk before
🥬 Swiss Chard	Start indoors	February 18 – April 7	5 wk before
🥬 Arugula	Direct sow	February 25 – April 14	4 wk before
🥬 Baby Salad Greens	Direct sow	February 25 – April 14	4 wk before
🥕 Beets	Direct sow	February 25 – April 14	4 wk before
🧅 Green Onions	Direct sow	February 25 – April 14	4 wk before
🥬 Mustard Greens	Direct sow	February 25 – April 14	4 wk before
🌶️ Okra	Start indoors	February 25 – April 14	4 wk before
🌱 Radishes	Direct sow	February 25 – April 14	4 wk before
🥔 Turnips	Direct sow	February 25 – April 14	4 wk before
🥬 Cabbage	Set out	March 4 – April 21	3 wk before
🥕 Carrots	Direct sow	March 4 – April 21	3 wk before
🥬 Collards	Direct sow	March 4 – April 21	3 wk before
🥬 Collards	Set out	March 4 – April 21	3 wk before
🥒 Cucumbers	Start indoors	March 4 – April 21	3 wk before
🧅 Green Onions	Set out	March 4 – April 21	3 wk before
🥬 Kale	Direct sow	March 4 – April 21	3 wk before
🥬 Kale	Set out	March 4 – April 21	3 wk before
🥬 Kohlrabi	Direct sow	March 4 – April 21	3 wk before
🥬 Kohlrabi	Set out	March 4 – April 21	3 wk before
🥬 Leaf Lettuce	Direct sow	March 4 – April 21	3 wk before
🎃 Pumpkins	Start indoors	March 4 – April 21	3 wk before
🎃 Summer Squash	Start indoors	March 4 – April 21	3 wk before
🎃 Winter Squash	Start indoors	March 4 – April 21	3 wk before
🥒 Zucchini	Start indoors	March 4 – April 21	3 wk before
🥬 Bok Choy	Direct sow	March 11 – April 28	2 wk before
🥬 Bok Choy	Set out	March 11 – April 28	2 wk before
🥦 Broccoli	Set out	March 11 – April 28	2 wk before
🌿 Cilantro	Direct sow	March 11 – April 28	2 wk before
🥬 Leaf Lettuce	Set out	March 11 – April 28	2 wk before
🥬 Swiss Chard	Direct sow	March 11 – April 28	2 wk before
🥬 Swiss Chard	Set out	March 11 – April 28	2 wk before
🌿 Dill	Direct sow	March 18 – May 5	1 wk before
🫘 Bush Beans	Direct sow	April 1 – May 19	1 wk after
🥒 Cucumbers	Set out	April 1 – May 19	1 wk after
🎃 Pumpkins	Direct sow	April 1 – May 19	1 wk after
🎃 Pumpkins	Set out	April 1 – May 19	1 wk after
🎃 Summer Squash	Direct sow	April 1 – May 19	1 wk after
🎃 Summer Squash	Set out	April 1 – May 19	1 wk after
🌽 Sweet Corn	Direct sow	April 1 – May 19	1 wk after
🍅 Tomatoes	Set out	April 1 – May 19	1 wk after
🎃 Winter Squash	Direct sow	April 1 – May 19	1 wk after
🎃 Winter Squash	Set out	April 1 – May 19	1 wk after
🥒 Zucchini	Direct sow	April 1 – May 19	1 wk after
🥒 Zucchini	Set out	April 1 – May 19	1 wk after
🥒 Cucumbers	Direct sow	April 8 – May 26	2 wk after
🌶️ Okra	Direct sow	April 8 – May 26	2 wk after
🌶️ Okra	Set out	April 8 – May 26	2 wk after
🌶️ Peppers	Set out	April 8 – May 26	2 wk after
🫘 Southern Peas	Direct sow	April 8 – May 26	2 wk after
🍠 Sweet Potato	Set out	April 8 – May 26	2 wk after

Offsets are published guidance; the dates they land on are computed from measured NOAA normals. The seed-starting tool does this for your own ZIP code and counts the days.

What survives the winter changes across Umatilla County

Zone 7a carries 58 of 74 perennial edibles; zone 6b carries 51. The best number is not always the warmest zone — the count peaks in the middle and falls both ways, because the warm end loses plants to insufficient winter chill and summer heat, not to cold.

Hardiness ranges are a judgement, published by growers rather than measured; the zone they are compared against is measured. On a warm-end verdict, check with your local extension service — a coastal zone 8 and an inland zone 8 are not the same summer.

Cautious — shortens the seasonMedian across stationsOptimistic

Last spring freeze: Plan to June 2 to be careful. Median March 25 – May 12 across 7 stations; March 6 is the optimistic end.
First fall freeze: Plan to September 8 to be careful. Median September 27 – November 4 across 7 stations; November 19 is the optimistic end.

NOAA publishes these as probabilities, not averages — the middle figure is a median, so half of years fall either side of it. The cautious end is the 10% tail: in roughly nine years in ten the freeze falls on the safe side of it.

The 7 stations behind these numbers

All 7 NOAA stations whose normals this page quotes, spanning about 52 km north to south. Every one is named with its identifier in the station list below — this page does not single one out, because no one station speaks for a whole county.

A relative sketch, not a map with a projection: longitude is adjusted for latitude so the shape is not stretched, and there is no basemap. For the one station nearest a specific address, with its real distance, use the ZIP lookup above.

These are the stations this county's ZIP codes actually cite as nearest — not a claim that each one sits inside its boundary, since a rural ZIP legitimately reaches over it. Every figure above comes from them, and each is named so you can check it.

Station	NOAA ID	Last spring freeze	First fall freeze	Season
Hermiston 2 NW, OR	USC00353818	April 27	October 7	163 days
Hermiston Muni AP, OR	USW00004113	April 26	October 10	167 days
Mcnary Dam #2, OR	USC00355392	March 30	November 4	217 days
Milton Freewater, OR	USC00355593	March 25	October 29	218 days
Pendleton Branch Exp Stn, OR	USC00356540	May 12	September 27	135 days
Pendleton Dwtn, OR	USC00356541	April 22	October 9	170 days
Pilot Rock 1 SE, OR	USC00356634	May 7	October 4	147 days

These are medians, not averages — NOAA publishes freeze dates as a probability distribution, and half of years freeze later than the date shown.

Your own ZIP

Work out your own dates

This page describes a whole county. Every tool below answers for one ZIP code, which is the grain the underlying data is published at.

Other places to compare

Umatilla County sits in Oregon. That page carries the whole state's zone spread, its metro areas, and every other county in it with a page here.

More of Oregon

Counties with the same zones — 6b–7b

Matched on the exact zone set, not a dominant zone, so the winter answer on these pages really is the same one as here.

Gear

If you want to act on this

Each link opens an Amazon search rather than a product we picked. We have not tested these and do not rank them — the search is the honest version, and you choose.

Row cover and frost clothThe season here closes at the first fall freeze dated above — a cover buys back some of those days at the end.
MulchFor the perennials nearest their cold limit in zone 6b, where an insulated crown is what decides whether they come back.

As an Amazon Associate we earn from qualifying purchases. That costs you nothing extra, and it buys no influence over anything on this site: the dates come from NOAA normals and the zones from the USDA, and no product affects either.

Sources

Where these numbers come from

Hardiness zones are the USDA 2023 Plant Hardiness Zone Map, published per ZIP code by PRISM at Oregon State. Freeze dates and growing-season lengths are NOAA 1991–2020 Climate Normals, taken per station and cited above by name and NOAA ID.

County boundaries come from the Census ZCTA-to-county relation, which is what places each ZIP code — and which treats parishes, boroughs and census areas as county equivalents. No station is chosen to represent this county: every range above is taken across all of them and the count is stated, because picking one would be a judgement dressed as a measurement.