What USDA hardiness zone is Box Elder County, Utah?

Box Elder County, Utah spans USDA hardiness zones 6a to 7a. 50% of its ZIP codes are zone 6b, so there is no single zone for the county.

When is the last spring frost in Box Elder County, Utah?

The median last spring freeze runs April 24 – June 3 across the 8 NOAA weather stations serving Box Elder County, Utah, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Utah

Planting zones in Box Elder County, Utah

This county spans USDA zones 6a to 7a, so there is no single zone for Box Elder County and anyone who gives you one is rounding. 50% of its ZIP codes are zone 6b; the rest are not.

USDA zones 6a–7a 3 zones across 18 ZIP codes

ZIP codes 18 18 have a NOAA station within range

Weather stations 8 NOAA 1991–2020 normals, across 5,746 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Box Elder County, Utah 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 Box Elder County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 18 – October 17 across the 8 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around February 27 – April 8 — counted back from a last spring freeze of April 24 – June 3 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 8 stations agreeAt least one station

Every one of the 8 NOAA stations serving this county counts June 3 – September 18 as growing season (107 days). Widening to any single station gives April 24 – October 17 (176 days).

That is a 69-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

Box Elder 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 50% in zone 6b and wrong for the other 50%. Here is the actual split.

Zone	ZIP codes	Share
6b	9	50%
6a	8	44%
7a	1	6%

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 April 24 – June 3

First fall freeze September 18 – October 17

Across the 8 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 105–175 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 81.8–89.5 °F in June–August. Summer rain over the same months runs 2.0–2.8" across those 8 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 19% 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 Box Elder 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
84301	6b	Tremonton, UT	11.2 km
84302	6b	Brigham City Waste Plt, UT	6.8 km
84306	6a	Cutler Dam, UT	5.4 km
84307	6b	Brigham City 28 Wnw, UT	15.2 km
84309	6b	Tremonton, UT	5.4 km
84311	6a	Cutler Dam, UT	4.6 km
84312	6b	Tremonton, UT	7.4 km
84313	6b	Montello - 7Ne, NV	32.9 km
84314	6b	Tremonton, UT	9.0 km
84316	6a	Thiokol Propulsion F S, UT	6.8 km
84324	6a	Brigham City Waste Plt, UT	9.2 km
84329	6a	Rosette, UT	5.5 km
84330	6a	Cutler Dam, UT	12.4 km
84331	6a	Malad City, ID	23.6 km
84334	6b	Tremonton, UT	8.8 km
84336	6a	Brigham City 28 Wnw, UT	39.0 km
84337	6b	Tremonton, UT	10.1 km
84340	7a	Brigham City Waste Plt, UT	17.6 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 Box Elder County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 8 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	February 27 – April 8	8 wk before
🌶️ Peppers	Start indoors	February 27 – April 8	8 wk before
🥦 Broccoli	Start indoors	March 13 – April 22	6 wk before
🥬 Cabbage	Start indoors	March 13 – April 22	6 wk before
🥬 Collards	Start indoors	March 13 – April 22	6 wk before
🥬 Kale	Start indoors	March 13 – April 22	6 wk before
🥬 Leaf Lettuce	Start indoors	March 13 – April 22	6 wk before
🫛 Peas	Direct sow	March 13 – April 22	6 wk before
🥬 Spinach	Direct sow	March 13 – April 22	6 wk before
🍠 Sweet Potato	Start indoors	March 13 – April 22	6 wk before
🍅 Tomatoes	Start indoors	March 13 – April 22	6 wk before
🥬 Bok Choy	Start indoors	March 20 – April 29	5 wk before
🥬 Kohlrabi	Start indoors	March 20 – April 29	5 wk before
🥬 Swiss Chard	Start indoors	March 20 – April 29	5 wk before
🥬 Arugula	Direct sow	March 27 – May 6	4 wk before
🥬 Baby Salad Greens	Direct sow	March 27 – May 6	4 wk before
🥕 Beets	Direct sow	March 27 – May 6	4 wk before
🧅 Green Onions	Direct sow	March 27 – May 6	4 wk before
🥬 Mustard Greens	Direct sow	March 27 – May 6	4 wk before
🌶️ Okra	Start indoors	March 27 – May 6	4 wk before
🌱 Radishes	Direct sow	March 27 – May 6	4 wk before
🥔 Turnips	Direct sow	March 27 – May 6	4 wk before
🥬 Cabbage	Set out	April 3 – May 13	3 wk before
🥕 Carrots	Direct sow	April 3 – May 13	3 wk before
🥬 Collards	Direct sow	April 3 – May 13	3 wk before
🥬 Collards	Set out	April 3 – May 13	3 wk before
🥒 Cucumbers	Start indoors	April 3 – May 13	3 wk before
🧅 Green Onions	Set out	April 3 – May 13	3 wk before
🥬 Kale	Direct sow	April 3 – May 13	3 wk before
🥬 Kale	Set out	April 3 – May 13	3 wk before
🥬 Kohlrabi	Direct sow	April 3 – May 13	3 wk before
🥬 Kohlrabi	Set out	April 3 – May 13	3 wk before
🥬 Leaf Lettuce	Direct sow	April 3 – May 13	3 wk before
🎃 Pumpkins	Start indoors	April 3 – May 13	3 wk before
🎃 Summer Squash	Start indoors	April 3 – May 13	3 wk before
🎃 Winter Squash	Start indoors	April 3 – May 13	3 wk before
🥒 Zucchini	Start indoors	April 3 – May 13	3 wk before
🥬 Bok Choy	Direct sow	April 10 – May 20	2 wk before
🥬 Bok Choy	Set out	April 10 – May 20	2 wk before
🥦 Broccoli	Set out	April 10 – May 20	2 wk before
🌿 Cilantro	Direct sow	April 10 – May 20	2 wk before
🥬 Leaf Lettuce	Set out	April 10 – May 20	2 wk before
🥬 Swiss Chard	Direct sow	April 10 – May 20	2 wk before
🥬 Swiss Chard	Set out	April 10 – May 20	2 wk before
🌿 Dill	Direct sow	April 17 – May 27	1 wk before
🫘 Bush Beans	Direct sow	May 1 – June 10	1 wk after
🥒 Cucumbers	Set out	May 1 – June 10	1 wk after
🎃 Pumpkins	Direct sow	May 1 – June 10	1 wk after
🎃 Pumpkins	Set out	May 1 – June 10	1 wk after
🎃 Summer Squash	Direct sow	May 1 – June 10	1 wk after
🎃 Summer Squash	Set out	May 1 – June 10	1 wk after
🌽 Sweet Corn	Direct sow	May 1 – June 10	1 wk after
🍅 Tomatoes	Set out	May 1 – June 10	1 wk after
🎃 Winter Squash	Direct sow	May 1 – June 10	1 wk after
🎃 Winter Squash	Set out	May 1 – June 10	1 wk after
🥒 Zucchini	Direct sow	May 1 – June 10	1 wk after
🥒 Zucchini	Set out	May 1 – June 10	1 wk after
🥒 Cucumbers	Direct sow	May 8 – June 17	2 wk after
🌶️ Okra	Direct sow	May 8 – June 17	2 wk after
🌶️ Okra	Set out	May 8 – June 17	2 wk after
🌶️ Peppers	Set out	May 8 – June 17	2 wk after
🫘 Southern Peas	Direct sow	May 8 – June 17	2 wk after
🍠 Sweet Potato	Set out	May 8 – June 17	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 Box Elder County

Zone 7a carries 58 of 74 perennial edibles; zone 6a 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 22 to be careful. Median April 24 – June 3 across 8 stations; April 8 is the optimistic end.
First fall freeze: Plan to September 3 to be careful. Median September 18 – October 17 across 8 stations; November 1 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 8 stations behind these numbers

All 8 NOAA stations whose normals this page quotes, spanning about 92 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
Brigham City 28 Wnw, UT	USW00004138	May 12	October 5	144 days
Brigham City Waste Plt, UT	USC00420928	May 5	October 5	150 days
Cutler Dam, UT	USC00421918	May 3	October 12	160 days
Malad City, ID	USW00024151	May 22	September 20	116 days
Montello - 7Ne, NV	USC00265353	June 3	September 18	105 days
Rosette, UT	USC00427408	May 21	October 2	132 days
Thiokol Propulsion F S, UT	USC00428668	May 17	September 24	128 days
Tremonton, UT	USC00428817	April 24	October 17	175 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

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

More of Utah

Counties with the same zones — 6a–7a

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.

Trunk wrapZone 6a is cold enough that winter sun on a young trunk does more damage than the cold does.
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 6a, 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.