What USDA hardiness zone is Iroquois County, Illinois?

Iroquois County, Illinois spans USDA hardiness zones 5b to 6a. 65% of its ZIP codes are zone 5b, so there is no single zone for the county.

When is the last spring frost in Iroquois County, Illinois?

The median last spring freeze runs April 19 – April 25 across the 7 NOAA weather stations serving Iroquois County, Illinois, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Illinois

Planting zones in Iroquois County, Illinois

This county spans USDA zones 5b to 6a, so there is no single zone for Iroquois County and anyone who gives you one is rounding. 65% of its ZIP codes are zone 5b; the rest are not.

USDA zones 5b–6a 2 zones across 23 ZIP codes

ZIP codes 23 23 have a NOAA station within range

Weather stations 7 NOAA 1991–2020 normals, across 1,117 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Iroquois County, Illinois 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 Iroquois County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives October 12 – October 24 across the 7 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around February 22 – February 28 — counted back from a last spring freeze of April 19 – April 25 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 7 stations agreeAt least one station

Every one of the 7 NOAA stations serving this county counts April 25 – October 12 as growing season (170 days). Widening to any single station gives April 19 – October 24 (188 days).

Which zone you are in depends where you are

Iroquois 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 65% in zone 5b and wrong for the other 35%. Here is the actual split.

Zone	ZIP codes	Share
5b	15	65%
6a	8	35%

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 19 – April 25

First fall freeze October 12 – October 24

Across the 7 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 169–188 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 81.8–86 °F in June–August. Summer rain over the same months runs 11.8–13.7" 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. At the middle station that is covered, so watering in Iroquois County is for the gaps between storms rather than the whole season. The inches are NOAA's published normals; the inch a week is a rule of thumb, and it takes no account of a 83 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Iroquois 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
60911	5b	Watseka 2 NW, IL	21.0 km
60912	5b	Watseka 2 NW, IL	23.6 km
60918	6a	Paxton 2 Wsw, IL	18.4 km
60924	6a	Hoopeston, IL	19.9 km
60926	6a	Hoopeston, IL	15.7 km
60927	5b	Kankakee Metro Wastewater, IL	23.0 km
60928	5b	Watseka 2 NW, IL	9.7 km
60930	5b	Piper City, IL	17.0 km
60931	5b	Watseka 2 NW, IL	17.5 km
60938	5b	Piper City, IL	16.8 km
60939	6a	Hoopeston, IL	13.6 km
60945	5b	Watseka 2 NW, IL	14.0 km
60948	6a	Paxton 2 Wsw, IL	9.4 km
60951	5b	Watseka 2 NW, IL	13.9 km
60953	6a	Hoopeston, IL	18.1 km
60955	5b	Piper City, IL	17.7 km
60956	5b	Watseka 2 NW, IL	19.6 km
60966	5b	Kentland, IN	12.5 km
60967	5b	Boswell 4Wnw, IN	14.7 km
60968	6a	Piper City, IL	10.5 km
60970	5b	Watseka 2 NW, IL	1.1 km
60973	6a	Hoopeston, IL	8.0 km
60974	5b	Watseka 2 NW, IL	8.6 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 Iroquois County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 7 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	February 22 – February 28	8 wk before
🌶️ Peppers	Start indoors	February 22 – February 28	8 wk before
🥦 Broccoli	Start indoors	March 8 – March 14	6 wk before
🥬 Cabbage	Start indoors	March 8 – March 14	6 wk before
🥬 Collards	Start indoors	March 8 – March 14	6 wk before
🥬 Kale	Start indoors	March 8 – March 14	6 wk before
🥬 Leaf Lettuce	Start indoors	March 8 – March 14	6 wk before
🫛 Peas	Direct sow	March 8 – March 14	6 wk before
🥬 Spinach	Direct sow	March 8 – March 14	6 wk before
🍠 Sweet Potato	Start indoors	March 8 – March 14	6 wk before
🍅 Tomatoes	Start indoors	March 8 – March 14	6 wk before
🥬 Bok Choy	Start indoors	March 15 – March 21	5 wk before
🥬 Kohlrabi	Start indoors	March 15 – March 21	5 wk before
🥬 Swiss Chard	Start indoors	March 15 – March 21	5 wk before
🥬 Arugula	Direct sow	March 22 – March 28	4 wk before
🥬 Baby Salad Greens	Direct sow	March 22 – March 28	4 wk before
🥕 Beets	Direct sow	March 22 – March 28	4 wk before
🧅 Green Onions	Direct sow	March 22 – March 28	4 wk before
🥬 Mustard Greens	Direct sow	March 22 – March 28	4 wk before
🌶️ Okra	Start indoors	March 22 – March 28	4 wk before
🌱 Radishes	Direct sow	March 22 – March 28	4 wk before
🥔 Turnips	Direct sow	March 22 – March 28	4 wk before
🥬 Cabbage	Set out	March 29 – April 4	3 wk before
🥕 Carrots	Direct sow	March 29 – April 4	3 wk before
🥬 Collards	Direct sow	March 29 – April 4	3 wk before
🥬 Collards	Set out	March 29 – April 4	3 wk before
🥒 Cucumbers	Start indoors	March 29 – April 4	3 wk before
🧅 Green Onions	Set out	March 29 – April 4	3 wk before
🥬 Kale	Direct sow	March 29 – April 4	3 wk before
🥬 Kale	Set out	March 29 – April 4	3 wk before
🥬 Kohlrabi	Direct sow	March 29 – April 4	3 wk before
🥬 Kohlrabi	Set out	March 29 – April 4	3 wk before
🥬 Leaf Lettuce	Direct sow	March 29 – April 4	3 wk before
🎃 Pumpkins	Start indoors	March 29 – April 4	3 wk before
🎃 Summer Squash	Start indoors	March 29 – April 4	3 wk before
🎃 Winter Squash	Start indoors	March 29 – April 4	3 wk before
🥒 Zucchini	Start indoors	March 29 – April 4	3 wk before
🥬 Bok Choy	Direct sow	April 5 – April 11	2 wk before
🥬 Bok Choy	Set out	April 5 – April 11	2 wk before
🥦 Broccoli	Set out	April 5 – April 11	2 wk before
🌿 Cilantro	Direct sow	April 5 – April 11	2 wk before
🥬 Leaf Lettuce	Set out	April 5 – April 11	2 wk before
🥬 Swiss Chard	Direct sow	April 5 – April 11	2 wk before
🥬 Swiss Chard	Set out	April 5 – April 11	2 wk before
🌿 Dill	Direct sow	April 12 – April 18	1 wk before
🫘 Bush Beans	Direct sow	April 26 – May 2	1 wk after
🥒 Cucumbers	Set out	April 26 – May 2	1 wk after
🎃 Pumpkins	Direct sow	April 26 – May 2	1 wk after
🎃 Pumpkins	Set out	April 26 – May 2	1 wk after
🎃 Summer Squash	Direct sow	April 26 – May 2	1 wk after
🎃 Summer Squash	Set out	April 26 – May 2	1 wk after
🌽 Sweet Corn	Direct sow	April 26 – May 2	1 wk after
🍅 Tomatoes	Set out	April 26 – May 2	1 wk after
🎃 Winter Squash	Direct sow	April 26 – May 2	1 wk after
🎃 Winter Squash	Set out	April 26 – May 2	1 wk after
🥒 Zucchini	Direct sow	April 26 – May 2	1 wk after
🥒 Zucchini	Set out	April 26 – May 2	1 wk after
🥒 Cucumbers	Direct sow	May 3 – May 9	2 wk after
🌶️ Okra	Direct sow	May 3 – May 9	2 wk after
🌶️ Okra	Set out	May 3 – May 9	2 wk after
🌶️ Peppers	Set out	May 3 – May 9	2 wk after
🫘 Southern Peas	Direct sow	May 3 – May 9	2 wk after
🍠 Sweet Potato	Set out	May 3 – May 9	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 Iroquois County

Zone 6a carries 51 of 74 perennial edibles; zone 5b carries 48. 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 12 to be careful. Median April 19 – April 25 across 7 stations; April 5 is the optimistic end.
First fall freeze: Plan to September 26 to be careful. Median October 12 – October 24 across 7 stations; November 5 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 7 stations behind these numbers

All 7 NOAA stations whose normals this page quotes, spanning about 75 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
Boswell 4Wnw, IN	USC00120858	April 25	October 13	169 days
Hoopeston, IL	USC00114198	April 22	October 19	180 days
Kankakee Metro Wastewater, IL	USC00114603	April 19	October 24	188 days
Kentland, IN	USC00124527	April 23	October 14	175 days
Paxton 2 Wsw, IL	USC00116663	April 23	October 12	170 days
Piper City, IL	USC00116819	April 25	October 20	175 days
Watseka 2 NW, IL	USC00119021	April 24	October 16	174 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

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

More of Illinois

Counties with the same zones — 5b–6a

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 5b 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 5b, 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.