What USDA hardiness zone is New London County, Connecticut?

New London County, Connecticut spans USDA hardiness zones 6b to 7a. 63% of its ZIP codes are zone 6b, so there is no single zone for the county.

When is the last spring frost in New London County, Connecticut?

The median last spring freeze runs April 8 – April 30 across the 6 NOAA weather stations serving New London County, Connecticut, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Connecticut

Planting zones in New London County, Connecticut

This county spans USDA zones 6b to 7a, so there is no single zone for New London County and anyone who gives you one is rounding. 63% of its ZIP codes are zone 6b; the rest are not.

USDA zones 6b–7a 2 zones across 32 ZIP codes

ZIP codes 32 32 have a NOAA station within range

Weather stations 6 NOAA 1991–2020 normals, across 665 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes New London County, Connecticut 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 New London County is closing

Nothing in the 32-crop table still has time to mature here. The first fall freeze normally arrives October 13 – November 2 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 February 11 – March 5 — counted back from a last spring freeze of April 8 – April 30 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 April 30 – October 13 as growing season (166 days). Widening to any single station gives April 8 – November 2 (208 days).

That is a 42-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

New London 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 63% in zone 6b and wrong for the other 37%. Here is the actual split.

Zone	ZIP codes	Share
6b	20	63%
7a	12	38%

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 8 – April 30

First fall freeze October 13 – November 2

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 167–207 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 77.6–81.7 °F in June–August. Summer rain over the same months runs 9.9–12.4" 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 88% 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 New London 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
06249	6b	Willimantic Windham AP, CT	13.0 km
06254	6b	Norwich Public Utility Plt, CT	12.3 km
06320	7a	Groton New London AP, CT	5.0 km
06330	6b	Norwich Public Utility Plt, CT	12.1 km
06333	7a	Groton New London AP, CT	16.3 km
06334	6b	Norwich Public Utility Plt, CT	9.3 km
06335	7a	Groton, CT	9.5 km
06336	6b	Norwich Public Utility Plt, CT	12.4 km
06338	6b	Norwich Public Utility Plt, CT	10.3 km
06339	6b	Groton, CT	10.9 km
06340	7a	Groton, CT	0.5 km
06350	6b	Hampton, CT	13.3 km
06351	6b	Norwich Public Utility Plt, CT	12.0 km
06355	7a	Groton, CT	5.8 km
06357	7a	Groton New London AP, CT	14.2 km
06359	6b	Westerly State AP, RI	14.8 km
06360	6b	Norwich Public Utility Plt, CT	3.1 km
06365	6b	Norwich Public Utility Plt, CT	5.0 km
06370	6b	Norwich Public Utility Plt, CT	12.3 km
06371	7a	Groton New London AP, CT	23.2 km
06375	7a	Groton, CT	9.5 km
06376	7a	Groton New London AP, CT	17.4 km
06378	7a	Westerly State AP, RI	9.9 km
06379	7a	Westerly State AP, RI	4.8 km
06380	6b	Norwich Public Utility Plt, CT	4.2 km
06382	6b	Norwich Public Utility Plt, CT	8.7 km
06384	6b	Norwich Public Utility Plt, CT	20.3 km
06385	7a	Groton New London AP, CT	9.7 km
06389	6b	Norwich Public Utility Plt, CT	6.1 km
06415	6b	Norwich Public Utility Plt, CT	23.7 km
06420	6b	Norwich Public Utility Plt, CT	16.6 km
06439	6b	Norwich Public Utility Plt, CT	30.5 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 New London 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	February 11 – March 5	8 wk before
🌶️ Peppers	Start indoors	February 11 – March 5	8 wk before
🥦 Broccoli	Start indoors	February 25 – March 19	6 wk before
🥬 Cabbage	Start indoors	February 25 – March 19	6 wk before
🥬 Collards	Start indoors	February 25 – March 19	6 wk before
🥬 Kale	Start indoors	February 25 – March 19	6 wk before
🥬 Leaf Lettuce	Start indoors	February 25 – March 19	6 wk before
🫛 Peas	Direct sow	February 25 – March 19	6 wk before
🥬 Spinach	Direct sow	February 25 – March 19	6 wk before
🍠 Sweet Potato	Start indoors	February 25 – March 19	6 wk before
🍅 Tomatoes	Start indoors	February 25 – March 19	6 wk before
🥬 Bok Choy	Start indoors	March 4 – March 26	5 wk before
🥬 Kohlrabi	Start indoors	March 4 – March 26	5 wk before
🥬 Swiss Chard	Start indoors	March 4 – March 26	5 wk before
🥬 Arugula	Direct sow	March 11 – April 2	4 wk before
🥬 Baby Salad Greens	Direct sow	March 11 – April 2	4 wk before
🥕 Beets	Direct sow	March 11 – April 2	4 wk before
🧅 Green Onions	Direct sow	March 11 – April 2	4 wk before
🥬 Mustard Greens	Direct sow	March 11 – April 2	4 wk before
🌶️ Okra	Start indoors	March 11 – April 2	4 wk before
🌱 Radishes	Direct sow	March 11 – April 2	4 wk before
🥔 Turnips	Direct sow	March 11 – April 2	4 wk before
🥬 Cabbage	Set out	March 18 – April 9	3 wk before
🥕 Carrots	Direct sow	March 18 – April 9	3 wk before
🥬 Collards	Direct sow	March 18 – April 9	3 wk before
🥬 Collards	Set out	March 18 – April 9	3 wk before
🥒 Cucumbers	Start indoors	March 18 – April 9	3 wk before
🧅 Green Onions	Set out	March 18 – April 9	3 wk before
🥬 Kale	Direct sow	March 18 – April 9	3 wk before
🥬 Kale	Set out	March 18 – April 9	3 wk before
🥬 Kohlrabi	Direct sow	March 18 – April 9	3 wk before
🥬 Kohlrabi	Set out	March 18 – April 9	3 wk before
🥬 Leaf Lettuce	Direct sow	March 18 – April 9	3 wk before
🎃 Pumpkins	Start indoors	March 18 – April 9	3 wk before
🎃 Summer Squash	Start indoors	March 18 – April 9	3 wk before
🎃 Winter Squash	Start indoors	March 18 – April 9	3 wk before
🥒 Zucchini	Start indoors	March 18 – April 9	3 wk before
🥬 Bok Choy	Direct sow	March 25 – April 16	2 wk before
🥬 Bok Choy	Set out	March 25 – April 16	2 wk before
🥦 Broccoli	Set out	March 25 – April 16	2 wk before
🌿 Cilantro	Direct sow	March 25 – April 16	2 wk before
🥬 Leaf Lettuce	Set out	March 25 – April 16	2 wk before
🥬 Swiss Chard	Direct sow	March 25 – April 16	2 wk before
🥬 Swiss Chard	Set out	March 25 – April 16	2 wk before
🌿 Dill	Direct sow	April 1 – April 23	1 wk before
🫘 Bush Beans	Direct sow	April 15 – May 7	1 wk after
🥒 Cucumbers	Set out	April 15 – May 7	1 wk after
🎃 Pumpkins	Direct sow	April 15 – May 7	1 wk after
🎃 Pumpkins	Set out	April 15 – May 7	1 wk after
🎃 Summer Squash	Direct sow	April 15 – May 7	1 wk after
🎃 Summer Squash	Set out	April 15 – May 7	1 wk after
🌽 Sweet Corn	Direct sow	April 15 – May 7	1 wk after
🍅 Tomatoes	Set out	April 15 – May 7	1 wk after
🎃 Winter Squash	Direct sow	April 15 – May 7	1 wk after
🎃 Winter Squash	Set out	April 15 – May 7	1 wk after
🥒 Zucchini	Direct sow	April 15 – May 7	1 wk after
🥒 Zucchini	Set out	April 15 – May 7	1 wk after
🥒 Cucumbers	Direct sow	April 22 – May 14	2 wk after
🌶️ Okra	Direct sow	April 22 – May 14	2 wk after
🌶️ Okra	Set out	April 22 – May 14	2 wk after
🌶️ Peppers	Set out	April 22 – May 14	2 wk after
🫘 Southern Peas	Direct sow	April 22 – May 14	2 wk after
🍠 Sweet Potato	Set out	April 22 – May 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 New London County

Zone 7a carries 58 of 74 perennial edibles; zone 6b carries 51. 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 11 to be careful. Median April 8 – April 30 across 6 stations; March 28 is the optimistic end.
First fall freeze: Plan to October 1 to be careful. Median October 13 – November 2 across 6 stations; November 15 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 49 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
Groton New London AP, CT	USW00014707	April 16	October 28	194 days
Groton, CT	USC00063207	April 8	November 2	207 days
Hampton, CT	USC00063420	April 30	October 15	167 days
Norwich Public Utility Plt, CT	USC00065910	April 14	October 24	192 days
Westerly State AP, RI	USW00014794	April 11	October 31	201 days
Willimantic Windham AP, CT	USW00054767	April 28	October 13	167 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

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

More of Connecticut

Counties with the same zones — 6b–7a

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.

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 6b, 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.