What USDA hardiness zone is Aitkin County, Minnesota?

Every ZIP code in Aitkin County, Minnesota is USDA hardiness zone 4a, from the USDA 2023 Plant Hardiness Zone Map.

When is the last spring frost in Aitkin County, Minnesota?

The median last spring freeze runs May 7 – May 31 across the 5 NOAA weather stations serving Aitkin County, Minnesota, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Minnesota

Planting zones in Aitkin County, Minnesota

Every ZIP code in this county is USDA zone 4a — so unlike most of the places people look up, there is one right answer here and it holds wherever you are in the county.

USDA zone 4a The same in all 9 ZIP codes

ZIP codes 9 9 have a NOAA station within range

Weather stations 5 NOAA 1991–2020 normals, across 1,822 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Aitkin County, Minnesota 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 Aitkin County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 18 – October 3 across the 5 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around March 12 – April 5 — counted back from a last spring freeze of May 7 – May 31 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 5 stations agreeAt least one station

Every one of the 5 NOAA stations serving this county counts May 31 – September 18 as growing season (110 days). Widening to any single station gives May 7 – October 3 (149 days).

That is a 39-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.

Your freeze dates

Last spring freeze May 7 – May 31

First fall freeze September 18 – October 3

Across the 5 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 107–148 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 74.3–76.9 °F in June–August. Summer rain over the same months runs 12.3–13.2" 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 95% 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 76 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Aitkin 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
55748	4a	Pokegama Dam, MN	28.6 km
55752	4a	Sandy Lake Dam Libby, MN	18.2 km
55760	4a	Sandy Lake Dam Libby, MN	17.7 km
55785	4a	Sandy Lake Dam Libby, MN	34.3 km
55787	4a	Wright 3 E, MN	12.6 km
56342	4a	Isle 12N, MN	18.2 km
56350	4a	Isle 12N, MN	20.9 km
56431	4a	Aitkin 2E, MN	4.6 km
56469	4a	Sandy Lake Dam Libby, MN	18.4 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 Aitkin County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 5 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	March 12 – April 5	8 wk before
🌶️ Peppers	Start indoors	March 12 – April 5	8 wk before
🥦 Broccoli	Start indoors	March 26 – April 19	6 wk before
🥬 Cabbage	Start indoors	March 26 – April 19	6 wk before
🥬 Collards	Start indoors	March 26 – April 19	6 wk before
🥬 Kale	Start indoors	March 26 – April 19	6 wk before
🥬 Leaf Lettuce	Start indoors	March 26 – April 19	6 wk before
🫛 Peas	Direct sow	March 26 – April 19	6 wk before
🥬 Spinach	Direct sow	March 26 – April 19	6 wk before
🍠 Sweet Potato	Start indoors	March 26 – April 19	6 wk before
🍅 Tomatoes	Start indoors	March 26 – April 19	6 wk before
🥬 Bok Choy	Start indoors	April 2 – April 26	5 wk before
🥬 Kohlrabi	Start indoors	April 2 – April 26	5 wk before
🥬 Swiss Chard	Start indoors	April 2 – April 26	5 wk before
🥬 Arugula	Direct sow	April 9 – May 3	4 wk before
🥬 Baby Salad Greens	Direct sow	April 9 – May 3	4 wk before
🥕 Beets	Direct sow	April 9 – May 3	4 wk before
🧅 Green Onions	Direct sow	April 9 – May 3	4 wk before
🥬 Mustard Greens	Direct sow	April 9 – May 3	4 wk before
🌶️ Okra	Start indoors	April 9 – May 3	4 wk before
🌱 Radishes	Direct sow	April 9 – May 3	4 wk before
🥔 Turnips	Direct sow	April 9 – May 3	4 wk before
🥬 Cabbage	Set out	April 16 – May 10	3 wk before
🥕 Carrots	Direct sow	April 16 – May 10	3 wk before
🥬 Collards	Direct sow	April 16 – May 10	3 wk before
🥬 Collards	Set out	April 16 – May 10	3 wk before
🥒 Cucumbers	Start indoors	April 16 – May 10	3 wk before
🧅 Green Onions	Set out	April 16 – May 10	3 wk before
🥬 Kale	Direct sow	April 16 – May 10	3 wk before
🥬 Kale	Set out	April 16 – May 10	3 wk before
🥬 Kohlrabi	Direct sow	April 16 – May 10	3 wk before
🥬 Kohlrabi	Set out	April 16 – May 10	3 wk before
🥬 Leaf Lettuce	Direct sow	April 16 – May 10	3 wk before
🎃 Pumpkins	Start indoors	April 16 – May 10	3 wk before
🎃 Summer Squash	Start indoors	April 16 – May 10	3 wk before
🎃 Winter Squash	Start indoors	April 16 – May 10	3 wk before
🥒 Zucchini	Start indoors	April 16 – May 10	3 wk before
🥬 Bok Choy	Direct sow	April 23 – May 17	2 wk before
🥬 Bok Choy	Set out	April 23 – May 17	2 wk before
🥦 Broccoli	Set out	April 23 – May 17	2 wk before
🌿 Cilantro	Direct sow	April 23 – May 17	2 wk before
🥬 Leaf Lettuce	Set out	April 23 – May 17	2 wk before
🥬 Swiss Chard	Direct sow	April 23 – May 17	2 wk before
🥬 Swiss Chard	Set out	April 23 – May 17	2 wk before
🌿 Dill	Direct sow	April 30 – May 24	1 wk before
🫘 Bush Beans	Direct sow	May 14 – June 7	1 wk after
🥒 Cucumbers	Set out	May 14 – June 7	1 wk after
🎃 Pumpkins	Direct sow	May 14 – June 7	1 wk after
🎃 Pumpkins	Set out	May 14 – June 7	1 wk after
🎃 Summer Squash	Direct sow	May 14 – June 7	1 wk after
🎃 Summer Squash	Set out	May 14 – June 7	1 wk after
🌽 Sweet Corn	Direct sow	May 14 – June 7	1 wk after
🍅 Tomatoes	Set out	May 14 – June 7	1 wk after
🎃 Winter Squash	Direct sow	May 14 – June 7	1 wk after
🎃 Winter Squash	Set out	May 14 – June 7	1 wk after
🥒 Zucchini	Direct sow	May 14 – June 7	1 wk after
🥒 Zucchini	Set out	May 14 – June 7	1 wk after
🥒 Cucumbers	Direct sow	May 21 – June 14	2 wk after
🌶️ Okra	Direct sow	May 21 – June 14	2 wk after
🌶️ Okra	Set out	May 21 – June 14	2 wk after
🌶️ Peppers	Set out	May 21 – June 14	2 wk after
🫘 Southern Peas	Direct sow	May 21 – June 14	2 wk after
🍠 Sweet Potato	Set out	May 21 – June 14	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 lives through a zone 4a winter

Of 74 perennial edibles, 34 come through a zone 4a winter — and 0 fail here for being too warm rather than too cold, needing more winter chill than this county gets or more heat than they tolerate. Among the ones that work: Cranberry, Honeyberry, Lingonberry, Apple, Aronia, Black Currant, Elderberry, Gooseberry.

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 20 to be careful. Median May 7 – May 31 across 5 stations; April 26 is the optimistic end.
First fall freeze: Plan to September 1 to be careful. Median September 18 – October 3 across 5 stations; October 17 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 5 stations behind these numbers

All 5 NOAA stations whose normals this page quotes, spanning about 103 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
Aitkin 2E, MN	USC00210059	May 16	September 28	133 days
Isle 12N, MN	USC00214103	May 10	October 3	144 days
Pokegama Dam, MN	USC00216612	May 16	October 1	138 days
Sandy Lake Dam Libby, MN	USC00217460	May 7	October 3	148 days
Wright 3 E, MN	USC00219173	May 31	September 18	107 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

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

More of Minnesota

Counties with the same zones — 4a

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 4a 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 4a, 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.