What USDA hardiness zone is Koochiching County, Minnesota?

Koochiching County, Minnesota spans USDA hardiness zones 3a to 3b. 82% of its ZIP codes are zone 3b, so there is no single zone for the county.

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

The median last spring freeze runs May 16 – June 2 across the 6 NOAA weather stations serving Koochiching County, Minnesota, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Minnesota

Planting zones in Koochiching County, Minnesota

This county spans USDA zones 3a to 3b, so there is no single zone for Koochiching County and anyone who gives you one is rounding. 82% of its ZIP codes are zone 3b; the rest are not.

USDA zones 3a–3b 2 zones across 11 ZIP codes

ZIP codes 11 11 have a NOAA station within range

Weather stations 6 NOAA 1991–2020 normals, across 3,105 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Koochiching 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 Koochiching County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 13 – September 26 across the 6 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around March 21 – April 7 — counted back from a last spring freeze of May 16 – June 2 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 6 stations agreeAt least one station

Every one of the 6 NOAA stations serving this county counts June 2 – September 13 as growing season (103 days). Widening to any single station gives May 16 – September 26 (133 days).

That is a 30-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

Koochiching 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 82% in zone 3b and wrong for the other 18%. Here is the actual split.

Zone	ZIP codes	Share
3b	9	82%
3a	2	18%

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 16 – June 2

First fall freeze September 13 – September 26

Across the 6 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 102–131 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 73.4–75.7 °F in June–August. Summer rain over the same months runs 10.6–11.9" 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 86% 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 Koochiching 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
55772	3b	Orr 3E, MN	25.9 km
56627	3b	Big Falls, MN	18.4 km
56629	3b	Littlefork 10 SW, MN	36.5 km
56649	3b	Kabetogama, MN	16.2 km
56653	3b	Littlefork 10 SW, MN	14.4 km
56654	3a	Littlefork 10 SW, MN	19.3 km
56658	3b	Big Falls, MN	13.6 km
56660	3b	Northome 3S, MN	18.1 km
56661	3b	Northome 3S, MN	9.7 km
56668	3a	INTL Falls INTL AP, MN	7.1 km
56669	3b	Kabetogama, MN	12.7 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 Koochiching County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 6 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	March 21 – April 7	8 wk before
🌶️ Peppers	Start indoors	March 21 – April 7	8 wk before
🥦 Broccoli	Start indoors	April 4 – April 21	6 wk before
🥬 Cabbage	Start indoors	April 4 – April 21	6 wk before
🥬 Collards	Start indoors	April 4 – April 21	6 wk before
🥬 Kale	Start indoors	April 4 – April 21	6 wk before
🥬 Leaf Lettuce	Start indoors	April 4 – April 21	6 wk before
🫛 Peas	Direct sow	April 4 – April 21	6 wk before
🥬 Spinach	Direct sow	April 4 – April 21	6 wk before
🍠 Sweet Potato	Start indoors	April 4 – April 21	6 wk before
🍅 Tomatoes	Start indoors	April 4 – April 21	6 wk before
🥬 Bok Choy	Start indoors	April 11 – April 28	5 wk before
🥬 Kohlrabi	Start indoors	April 11 – April 28	5 wk before
🥬 Swiss Chard	Start indoors	April 11 – April 28	5 wk before
🥬 Arugula	Direct sow	April 18 – May 5	4 wk before
🥬 Baby Salad Greens	Direct sow	April 18 – May 5	4 wk before
🥕 Beets	Direct sow	April 18 – May 5	4 wk before
🧅 Green Onions	Direct sow	April 18 – May 5	4 wk before
🥬 Mustard Greens	Direct sow	April 18 – May 5	4 wk before
🌶️ Okra	Start indoors	April 18 – May 5	4 wk before
🌱 Radishes	Direct sow	April 18 – May 5	4 wk before
🥔 Turnips	Direct sow	April 18 – May 5	4 wk before
🥬 Cabbage	Set out	April 25 – May 12	3 wk before
🥕 Carrots	Direct sow	April 25 – May 12	3 wk before
🥬 Collards	Direct sow	April 25 – May 12	3 wk before
🥬 Collards	Set out	April 25 – May 12	3 wk before
🥒 Cucumbers	Start indoors	April 25 – May 12	3 wk before
🧅 Green Onions	Set out	April 25 – May 12	3 wk before
🥬 Kale	Direct sow	April 25 – May 12	3 wk before
🥬 Kale	Set out	April 25 – May 12	3 wk before
🥬 Kohlrabi	Direct sow	April 25 – May 12	3 wk before
🥬 Kohlrabi	Set out	April 25 – May 12	3 wk before
🥬 Leaf Lettuce	Direct sow	April 25 – May 12	3 wk before
🎃 Pumpkins	Start indoors	April 25 – May 12	3 wk before
🎃 Summer Squash	Start indoors	April 25 – May 12	3 wk before
🎃 Winter Squash	Start indoors	April 25 – May 12	3 wk before
🥒 Zucchini	Start indoors	April 25 – May 12	3 wk before
🥬 Bok Choy	Direct sow	May 2 – May 19	2 wk before
🥬 Bok Choy	Set out	May 2 – May 19	2 wk before
🥦 Broccoli	Set out	May 2 – May 19	2 wk before
🌿 Cilantro	Direct sow	May 2 – May 19	2 wk before
🥬 Leaf Lettuce	Set out	May 2 – May 19	2 wk before
🥬 Swiss Chard	Direct sow	May 2 – May 19	2 wk before
🥬 Swiss Chard	Set out	May 2 – May 19	2 wk before
🌿 Dill	Direct sow	May 9 – May 26	1 wk before
🫘 Bush Beans	Direct sow	May 23 – June 9	1 wk after
🥒 Cucumbers	Set out	May 23 – June 9	1 wk after
🎃 Pumpkins	Direct sow	May 23 – June 9	1 wk after
🎃 Pumpkins	Set out	May 23 – June 9	1 wk after
🎃 Summer Squash	Direct sow	May 23 – June 9	1 wk after
🎃 Summer Squash	Set out	May 23 – June 9	1 wk after
🌽 Sweet Corn	Direct sow	May 23 – June 9	1 wk after
🍅 Tomatoes	Set out	May 23 – June 9	1 wk after
🎃 Winter Squash	Direct sow	May 23 – June 9	1 wk after
🎃 Winter Squash	Set out	May 23 – June 9	1 wk after
🥒 Zucchini	Direct sow	May 23 – June 9	1 wk after
🥒 Zucchini	Set out	May 23 – June 9	1 wk after
🥒 Cucumbers	Direct sow	May 30 – June 16	2 wk after
🌶️ Okra	Direct sow	May 30 – June 16	2 wk after
🌶️ Okra	Set out	May 30 – June 16	2 wk after
🌶️ Peppers	Set out	May 30 – June 16	2 wk after
🫘 Southern Peas	Direct sow	May 30 – June 16	2 wk after
🍠 Sweet Potato	Set out	May 30 – June 16	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 Koochiching County

Zone 3a carries 17 of 74 perennial edibles; zone 3a carries 17.

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 17 to be careful. Median May 16 – June 2 across 6 stations; May 3 is the optimistic end.
First fall freeze: Plan to August 29 to be careful. Median September 13 – September 26 across 6 stations; October 11 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 6 stations behind these numbers

All 6 NOAA stations whose normals this page quotes, spanning about 81 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
Big Falls, MN	USC00210746	May 24	September 20	117 days
INTL Falls INTL AP, MN	USW00014918	May 29	September 13	109 days
Kabetogama, MN	USC00214191	May 28	September 16	111 days
Littlefork 10 SW, MN	USC00214809	May 23	September 21	118 days
Northome 3S, MN	USC00215989	May 16	September 26	131 days
Orr 3E, MN	USC00216211	June 2	September 15	102 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

Koochiching 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

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 3a 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 3a, 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.