What USDA hardiness zone is Grand County, Colorado?

Grand County, Colorado spans USDA hardiness zones 5a to 5b. 63% of its ZIP codes are zone 5a, so there is no single zone for the county.

When is the last spring frost in Grand County, Colorado?

The median last spring freeze runs May 30 – June 14 across the 4 NOAA weather stations serving Grand County, Colorado, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Colorado

Planting zones in Grand County, Colorado

This county spans USDA zones 5a to 5b, so there is no single zone for Grand County and anyone who gives you one is rounding. 63% of its ZIP codes are zone 5a; the rest are not.

USDA zones 5a–5b 2 zones across 8 ZIP codes

ZIP codes 8 8 have a NOAA station within range

Weather stations 4 NOAA 1991–2020 normals, across 1,846 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Grand County, Colorado 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 Grand County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 5 – September 19 across the 4 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around April 4 – April 19 — counted back from a last spring freeze of May 30 – June 14 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 4 stations agreeAt least one station

Every one of the 4 NOAA stations serving this county counts June 14 – September 5 as growing season (83 days). Widening to any single station gives May 30 – September 19 (112 days).

That is a 29-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

Grand County covers 2 hardiness zones. A guide that gives the county one zone has picked whichever is largest and rounded everyone else into it — fine for the 63% in zone 5a and wrong for the other 37%. Here is the actual split.

Zone	ZIP codes	Share
5a	5	63%
5b	3	38%

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 May 30 – June 14

First fall freeze September 5 – September 19

Across the 4 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 80–112 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 72.6–78.6 °F in June–August. Summer rain over the same months runs 3.6–6.2" across those 4 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 34% of it, so expect to make up the rest. The inches are NOAA's published normals; the inch a week is a rule of thumb, and it takes no account of a 77 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Grand 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
80442	5b	Grand Lake 6 Ssw, CO	29.0 km
80446	5a	Grand Lake 6 Ssw, CO	6.2 km
80447	5a	Grand Lake 6 Ssw, CO	12.9 km
80451	5b	Williams Fork Dam, CO	13.6 km
80459	5a	Kremmling, CO	11.5 km
80468	5a	Williams Fork Dam, CO	15.8 km
80478	5b	Grand Lake 6 Ssw, CO	18.1 km
80482	5a	Georgetown, CO	23.0 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 Grand County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 4 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	April 4 – April 19	8 wk before
🌶️ Peppers	Start indoors	April 4 – April 19	8 wk before
🥦 Broccoli	Start indoors	April 18 – May 3	6 wk before
🥬 Cabbage	Start indoors	April 18 – May 3	6 wk before
🥬 Collards	Start indoors	April 18 – May 3	6 wk before
🥬 Kale	Start indoors	April 18 – May 3	6 wk before
🥬 Leaf Lettuce	Start indoors	April 18 – May 3	6 wk before
🫛 Peas	Direct sow	April 18 – May 3	6 wk before
🥬 Spinach	Direct sow	April 18 – May 3	6 wk before
🍠 Sweet Potato	Start indoors	April 18 – May 3	6 wk before
🍅 Tomatoes	Start indoors	April 18 – May 3	6 wk before
🥬 Bok Choy	Start indoors	April 25 – May 10	5 wk before
🥬 Kohlrabi	Start indoors	April 25 – May 10	5 wk before
🥬 Swiss Chard	Start indoors	April 25 – May 10	5 wk before
🥬 Arugula	Direct sow	May 2 – May 17	4 wk before
🥬 Baby Salad Greens	Direct sow	May 2 – May 17	4 wk before
🥕 Beets	Direct sow	May 2 – May 17	4 wk before
🧅 Green Onions	Direct sow	May 2 – May 17	4 wk before
🥬 Mustard Greens	Direct sow	May 2 – May 17	4 wk before
🌶️ Okra	Start indoors	May 2 – May 17	4 wk before
🌱 Radishes	Direct sow	May 2 – May 17	4 wk before
🥔 Turnips	Direct sow	May 2 – May 17	4 wk before
🥬 Cabbage	Set out	May 9 – May 24	3 wk before
🥕 Carrots	Direct sow	May 9 – May 24	3 wk before
🥬 Collards	Direct sow	May 9 – May 24	3 wk before
🥬 Collards	Set out	May 9 – May 24	3 wk before
🥒 Cucumbers	Start indoors	May 9 – May 24	3 wk before
🧅 Green Onions	Set out	May 9 – May 24	3 wk before
🥬 Kale	Direct sow	May 9 – May 24	3 wk before
🥬 Kale	Set out	May 9 – May 24	3 wk before
🥬 Kohlrabi	Direct sow	May 9 – May 24	3 wk before
🥬 Kohlrabi	Set out	May 9 – May 24	3 wk before
🥬 Leaf Lettuce	Direct sow	May 9 – May 24	3 wk before
🎃 Pumpkins	Start indoors	May 9 – May 24	3 wk before
🎃 Summer Squash	Start indoors	May 9 – May 24	3 wk before
🎃 Winter Squash	Start indoors	May 9 – May 24	3 wk before
🥒 Zucchini	Start indoors	May 9 – May 24	3 wk before
🥬 Bok Choy	Direct sow	May 16 – May 31	2 wk before
🥬 Bok Choy	Set out	May 16 – May 31	2 wk before
🥦 Broccoli	Set out	May 16 – May 31	2 wk before
🌿 Cilantro	Direct sow	May 16 – May 31	2 wk before
🥬 Leaf Lettuce	Set out	May 16 – May 31	2 wk before
🥬 Swiss Chard	Direct sow	May 16 – May 31	2 wk before
🥬 Swiss Chard	Set out	May 16 – May 31	2 wk before
🌿 Dill	Direct sow	May 23 – June 7	1 wk before
🫘 Bush Beans	Direct sow	June 6 – June 21	1 wk after
🥒 Cucumbers	Set out	June 6 – June 21	1 wk after
🎃 Pumpkins	Direct sow	June 6 – June 21	1 wk after
🎃 Pumpkins	Set out	June 6 – June 21	1 wk after
🎃 Summer Squash	Direct sow	June 6 – June 21	1 wk after
🎃 Summer Squash	Set out	June 6 – June 21	1 wk after
🌽 Sweet Corn	Direct sow	June 6 – June 21	1 wk after
🍅 Tomatoes	Set out	June 6 – June 21	1 wk after
🎃 Winter Squash	Direct sow	June 6 – June 21	1 wk after
🎃 Winter Squash	Set out	June 6 – June 21	1 wk after
🥒 Zucchini	Direct sow	June 6 – June 21	1 wk after
🥒 Zucchini	Set out	June 6 – June 21	1 wk after
🥒 Cucumbers	Direct sow	June 13 – June 28	2 wk after
🌶️ Okra	Direct sow	June 13 – June 28	2 wk after
🌶️ Okra	Set out	June 13 – June 28	2 wk after
🌶️ Peppers	Set out	June 13 – June 28	2 wk after
🫘 Southern Peas	Direct sow	June 13 – June 28	2 wk after
🍠 Sweet Potato	Set out	June 13 – June 28	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 Grand County

Zone 5a carries 48 of 74 perennial edibles; zone 5a carries 48.

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 30 to be careful. Median May 30 – June 14 across 4 stations; May 17 is the optimistic end.
First fall freeze: Plan to August 21 to be careful. Median September 5 – September 19 across 4 stations; September 30 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 4 stations behind these numbers

All 4 NOAA stations whose normals this page quotes, spanning about 53 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
Georgetown, CO	USC00053261	May 30	September 19	112 days
Grand Lake 6 Ssw, CO	USC00053500	June 13	September 7	84 days
Kremmling, CO	USC00054664	June 14	September 5	80 days
Williams Fork Dam, CO	USC00059096	June 12	September 10	89 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

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

More of Colorado

Counties with the same zones — 5a–5b

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 5a 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 5a, 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.