What USDA hardiness zone is Coos County, New Hampshire?

Coos County, New Hampshire spans USDA hardiness zones 4a to 5a. 50% of its ZIP codes are zone 4b, so there is no single zone for the county.

When is the last spring frost in Coos County, New Hampshire?

The median last spring freeze runs May 8 – May 31 across the 11 NOAA weather stations serving Coos County, New Hampshire, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

New Hampshire

Planting zones in Coos County, New Hampshire

This county spans USDA zones 4a to 5a, so there is no single zone for Coos County and anyone who gives you one is rounding. 50% of its ZIP codes are zone 4b; the rest are not.

USDA zones 4a–5a 3 zones across 14 ZIP codes

ZIP codes 14 14 have a NOAA station within range

Weather stations 11 NOAA 1991–2020 normals, across 1,795 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Coos County, New Hampshire 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 Coos County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives September 19 – October 1 across the 11 NOAA stations serving this county .

Your next season already has a date

The first job of it is 🧅 Green Onions, start indoors, around March 13 – April 5 — counted back from a last spring freeze of May 8 – 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 11 stations agreeAt least one station

Every one of the 11 NOAA stations serving this county counts May 31 – September 19 as growing season (111 days). Widening to any single station gives May 8 – October 1 (146 days).

That is a 35-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

Coos County covers 3 hardiness zones. A guide that gives the county one zone has picked whichever is largest and rounded everyone else into it — fine for the 50% in zone 4b and wrong for the other 50%. Here is the actual split.

Zone	ZIP codes	Share
4b	7	50%
4a	4	29%
5a	3	21%

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 8 – May 31

First fall freeze September 19 – October 1

Across the 11 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 112–146 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 73–77.8 °F in June–August. Summer rain over the same months runs 12.1–16.5" across those 11 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 97% 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 Coos 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
03570	4b	Berlin, NH	6.5 km
03575	5a	Whitefield Mt Washington AP, NH	12.8 km
03576	4a	Colebrook 3Sw, NH	13.3 km
03581	5a	Gorham AP, NH	9.0 km
03582	4b	York Pond, NH	10.8 km
03583	4b	Jefferson, NH	3.8 km
03584	4b	Lancaster, NH	2.4 km
03588	4b	Berlin Muni AP, NH	5.8 km
03590	4a	N Stratford, NH	5.9 km
03592	4a	First Connecticut Lake, NH	3.7 km
03593	5a	Pinkham Notch, NH	6.1 km
03595	4b	Whitefield Mt Washington AP, NH	7.9 km
03597	4a	N Stratford, NH	17.6 km
03598	4b	Whitefield Mt Washington AP, NH	6.8 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 Coos County

Every date below is anchored on the last spring freeze at each station and reported as a range across all 11 of them, because no one station speaks for the county.

Crop	Job	When	Offset
🧅 Green Onions	Start indoors	March 13 – April 5	8 wk before
🌶️ Peppers	Start indoors	March 13 – April 5	8 wk before
🥦 Broccoli	Start indoors	March 27 – April 19	6 wk before
🥬 Cabbage	Start indoors	March 27 – April 19	6 wk before
🥬 Collards	Start indoors	March 27 – April 19	6 wk before
🥬 Kale	Start indoors	March 27 – April 19	6 wk before
🥬 Leaf Lettuce	Start indoors	March 27 – April 19	6 wk before
🫛 Peas	Direct sow	March 27 – April 19	6 wk before
🥬 Spinach	Direct sow	March 27 – April 19	6 wk before
🍠 Sweet Potato	Start indoors	March 27 – April 19	6 wk before
🍅 Tomatoes	Start indoors	March 27 – April 19	6 wk before
🥬 Bok Choy	Start indoors	April 3 – April 26	5 wk before
🥬 Kohlrabi	Start indoors	April 3 – April 26	5 wk before
🥬 Swiss Chard	Start indoors	April 3 – April 26	5 wk before
🥬 Arugula	Direct sow	April 10 – May 3	4 wk before
🥬 Baby Salad Greens	Direct sow	April 10 – May 3	4 wk before
🥕 Beets	Direct sow	April 10 – May 3	4 wk before
🧅 Green Onions	Direct sow	April 10 – May 3	4 wk before
🥬 Mustard Greens	Direct sow	April 10 – May 3	4 wk before
🌶️ Okra	Start indoors	April 10 – May 3	4 wk before
🌱 Radishes	Direct sow	April 10 – May 3	4 wk before
🥔 Turnips	Direct sow	April 10 – May 3	4 wk before
🥬 Cabbage	Set out	April 17 – May 10	3 wk before
🥕 Carrots	Direct sow	April 17 – May 10	3 wk before
🥬 Collards	Direct sow	April 17 – May 10	3 wk before
🥬 Collards	Set out	April 17 – May 10	3 wk before
🥒 Cucumbers	Start indoors	April 17 – May 10	3 wk before
🧅 Green Onions	Set out	April 17 – May 10	3 wk before
🥬 Kale	Direct sow	April 17 – May 10	3 wk before
🥬 Kale	Set out	April 17 – May 10	3 wk before
🥬 Kohlrabi	Direct sow	April 17 – May 10	3 wk before
🥬 Kohlrabi	Set out	April 17 – May 10	3 wk before
🥬 Leaf Lettuce	Direct sow	April 17 – May 10	3 wk before
🎃 Pumpkins	Start indoors	April 17 – May 10	3 wk before
🎃 Summer Squash	Start indoors	April 17 – May 10	3 wk before
🎃 Winter Squash	Start indoors	April 17 – May 10	3 wk before
🥒 Zucchini	Start indoors	April 17 – May 10	3 wk before
🥬 Bok Choy	Direct sow	April 24 – May 17	2 wk before
🥬 Bok Choy	Set out	April 24 – May 17	2 wk before
🥦 Broccoli	Set out	April 24 – May 17	2 wk before
🌿 Cilantro	Direct sow	April 24 – May 17	2 wk before
🥬 Leaf Lettuce	Set out	April 24 – May 17	2 wk before
🥬 Swiss Chard	Direct sow	April 24 – May 17	2 wk before
🥬 Swiss Chard	Set out	April 24 – May 17	2 wk before
🌿 Dill	Direct sow	May 1 – May 24	1 wk before
🫘 Bush Beans	Direct sow	May 15 – June 7	1 wk after
🥒 Cucumbers	Set out	May 15 – June 7	1 wk after
🎃 Pumpkins	Direct sow	May 15 – June 7	1 wk after
🎃 Pumpkins	Set out	May 15 – June 7	1 wk after
🎃 Summer Squash	Direct sow	May 15 – June 7	1 wk after
🎃 Summer Squash	Set out	May 15 – June 7	1 wk after
🌽 Sweet Corn	Direct sow	May 15 – June 7	1 wk after
🍅 Tomatoes	Set out	May 15 – June 7	1 wk after
🎃 Winter Squash	Direct sow	May 15 – June 7	1 wk after
🎃 Winter Squash	Set out	May 15 – June 7	1 wk after
🥒 Zucchini	Direct sow	May 15 – June 7	1 wk after
🥒 Zucchini	Set out	May 15 – June 7	1 wk after
🥒 Cucumbers	Direct sow	May 22 – June 14	2 wk after
🌶️ Okra	Direct sow	May 22 – June 14	2 wk after
🌶️ Okra	Set out	May 22 – June 14	2 wk after
🌶️ Peppers	Set out	May 22 – June 14	2 wk after
🫘 Southern Peas	Direct sow	May 22 – June 14	2 wk after
🍠 Sweet Potato	Set out	May 22 – 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 survives the winter changes across Coos County

Zone 5a carries 48 of 74 perennial edibles; zone 4a 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 June 14 to be careful. Median May 8 – May 31 across 11 stations; April 27 is the optimistic end.
First fall freeze: Plan to September 5 to be careful. Median September 19 – October 1 across 11 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 11 stations behind these numbers

All 11 NOAA stations whose normals this page quotes, spanning about 92 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
Berlin Muni AP, NH	USW00094700	May 30	September 19	112 days
Berlin, NH	USC00270690	May 14	September 30	135 days
Colebrook 3Sw, NH	USC00271647	May 31	September 21	112 days
First Connecticut Lake, NH	USC00272999	May 25	September 24	121 days
Gorham AP, NH	USC00273488	May 14	September 26	133 days
Jefferson, NH	USC00274329	May 8	October 1	146 days
Lancaster, NH	USC00274556	May 18	September 30	132 days
N Stratford, NH	USC00276234	May 19	September 29	131 days
Pinkham Notch, NH	USC00276818	May 18	October 1	135 days
Whitefield Mt Washington AP, NH	USW00054728	May 27	September 19	116 days
York Pond, NH	USC00279966	May 23	September 22	122 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

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

More of New Hampshire

Counties with the same zones — 4a–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 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.