What USDA hardiness zone is Portage County, Wisconsin?

Portage County, Wisconsin spans USDA hardiness zones 4b to 5a. 64% of its ZIP codes are zone 4b, so there is no single zone for the county.

When is the last spring frost in Portage County, Wisconsin?

The median last spring freeze runs May 4 – May 10 across the 4 NOAA weather stations serving Portage County, Wisconsin, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Wisconsin

Planting zones in Portage County, Wisconsin

This county spans USDA zones 4b to 5a, so there is no single zone for Portage County and anyone who gives you one is rounding. 64% of its ZIP codes are zone 4b; the rest are not.

USDA zones 4b–5a 2 zones across 11 ZIP codes

ZIP codes 11 11 have a NOAA station within range

Weather stations 4 NOAA 1991–2020 normals, across 801 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Portage County, Wisconsin 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 Portage County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives October 3 – October 7 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 March 9 – March 15 — counted back from a last spring freeze of May 4 – May 10 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 May 10 – October 3 as growing season (146 days). Widening to any single station gives May 4 – October 7 (156 days).

Which zone you are in depends where you are

Portage 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 64% in zone 4b and wrong for the other 36%. Here is the actual split.

Zone	ZIP codes	Share
4b	7	64%
5a	4	36%

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 4 – May 10

First fall freeze October 3 – October 7

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 146–155 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 77.8–79.7 °F in June–August. Summer rain over the same months runs 12.1–13.1" 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 96% 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 79 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Portage 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
54406	5a	Waupaca, WI	20.5 km
54407	5a	Stevens Pt, WI	24.2 km
54423	4b	Stevens Pt, WI	14.7 km
54443	4b	Stevens Pt, WI	17.1 km
54458	5a	Stevens Pt, WI	22.2 km
54467	4b	Stevens Pt, WI	11.4 km
54473	4b	Rosholt 9 Nne, WI	14.0 km
54481	5a	Stevens Pt, WI	5.0 km
54482	4b	Stevens Pt, WI	7.4 km
54909	4b	Hancock Exp Farm, WI	22.5 km
54921	4b	Hancock Exp Farm, WI	20.0 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 Portage 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	March 9 – March 15	8 wk before
🌶️ Peppers	Start indoors	March 9 – March 15	8 wk before
🥦 Broccoli	Start indoors	March 23 – March 29	6 wk before
🥬 Cabbage	Start indoors	March 23 – March 29	6 wk before
🥬 Collards	Start indoors	March 23 – March 29	6 wk before
🥬 Kale	Start indoors	March 23 – March 29	6 wk before
🥬 Leaf Lettuce	Start indoors	March 23 – March 29	6 wk before
🫛 Peas	Direct sow	March 23 – March 29	6 wk before
🥬 Spinach	Direct sow	March 23 – March 29	6 wk before
🍠 Sweet Potato	Start indoors	March 23 – March 29	6 wk before
🍅 Tomatoes	Start indoors	March 23 – March 29	6 wk before
🥬 Bok Choy	Start indoors	March 30 – April 5	5 wk before
🥬 Kohlrabi	Start indoors	March 30 – April 5	5 wk before
🥬 Swiss Chard	Start indoors	March 30 – April 5	5 wk before
🥬 Arugula	Direct sow	April 6 – April 12	4 wk before
🥬 Baby Salad Greens	Direct sow	April 6 – April 12	4 wk before
🥕 Beets	Direct sow	April 6 – April 12	4 wk before
🧅 Green Onions	Direct sow	April 6 – April 12	4 wk before
🥬 Mustard Greens	Direct sow	April 6 – April 12	4 wk before
🌶️ Okra	Start indoors	April 6 – April 12	4 wk before
🌱 Radishes	Direct sow	April 6 – April 12	4 wk before
🥔 Turnips	Direct sow	April 6 – April 12	4 wk before
🥬 Cabbage	Set out	April 13 – April 19	3 wk before
🥕 Carrots	Direct sow	April 13 – April 19	3 wk before
🥬 Collards	Direct sow	April 13 – April 19	3 wk before
🥬 Collards	Set out	April 13 – April 19	3 wk before
🥒 Cucumbers	Start indoors	April 13 – April 19	3 wk before
🧅 Green Onions	Set out	April 13 – April 19	3 wk before
🥬 Kale	Direct sow	April 13 – April 19	3 wk before
🥬 Kale	Set out	April 13 – April 19	3 wk before
🥬 Kohlrabi	Direct sow	April 13 – April 19	3 wk before
🥬 Kohlrabi	Set out	April 13 – April 19	3 wk before
🥬 Leaf Lettuce	Direct sow	April 13 – April 19	3 wk before
🎃 Pumpkins	Start indoors	April 13 – April 19	3 wk before
🎃 Summer Squash	Start indoors	April 13 – April 19	3 wk before
🎃 Winter Squash	Start indoors	April 13 – April 19	3 wk before
🥒 Zucchini	Start indoors	April 13 – April 19	3 wk before
🥬 Bok Choy	Direct sow	April 20 – April 26	2 wk before
🥬 Bok Choy	Set out	April 20 – April 26	2 wk before
🥦 Broccoli	Set out	April 20 – April 26	2 wk before
🌿 Cilantro	Direct sow	April 20 – April 26	2 wk before
🥬 Leaf Lettuce	Set out	April 20 – April 26	2 wk before
🥬 Swiss Chard	Direct sow	April 20 – April 26	2 wk before
🥬 Swiss Chard	Set out	April 20 – April 26	2 wk before
🌿 Dill	Direct sow	April 27 – May 3	1 wk before
🫘 Bush Beans	Direct sow	May 11 – May 17	1 wk after
🥒 Cucumbers	Set out	May 11 – May 17	1 wk after
🎃 Pumpkins	Direct sow	May 11 – May 17	1 wk after
🎃 Pumpkins	Set out	May 11 – May 17	1 wk after
🎃 Summer Squash	Direct sow	May 11 – May 17	1 wk after
🎃 Summer Squash	Set out	May 11 – May 17	1 wk after
🌽 Sweet Corn	Direct sow	May 11 – May 17	1 wk after
🍅 Tomatoes	Set out	May 11 – May 17	1 wk after
🎃 Winter Squash	Direct sow	May 11 – May 17	1 wk after
🎃 Winter Squash	Set out	May 11 – May 17	1 wk after
🥒 Zucchini	Direct sow	May 11 – May 17	1 wk after
🥒 Zucchini	Set out	May 11 – May 17	1 wk after
🥒 Cucumbers	Direct sow	May 18 – May 24	2 wk after
🌶️ Okra	Direct sow	May 18 – May 24	2 wk after
🌶️ Okra	Set out	May 18 – May 24	2 wk after
🌶️ Peppers	Set out	May 18 – May 24	2 wk after
🫘 Southern Peas	Direct sow	May 18 – May 24	2 wk after
🍠 Sweet Potato	Set out	May 18 – May 24	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 Portage County

Zone 5a carries 48 of 74 perennial edibles; zone 4b carries 34. 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 May 24 to be careful. Median May 4 – May 10 across 4 stations; April 22 is the optimistic end.
First fall freeze: Plan to September 20 to be careful. Median October 3 – October 7 across 4 stations; October 22 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 70 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
Hancock Exp Farm, WI	USC00473405	May 10	October 3	146 days
Rosholt 9 Nne, WI	USC00477349	May 6	October 5	150 days
Stevens Pt, WI	USC00478171	May 4	October 7	155 days
Waupaca, WI	USC00478951	May 8	October 6	151 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

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

More of Wisconsin

Counties with the same zones — 4b–5a

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 4b 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 4b, 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.