What USDA hardiness zone is Middlesex County, Connecticut?

Middlesex County, Connecticut spans USDA hardiness zones 6b to 7a. 70% of its ZIP codes are zone 6b, so there is no single zone for the county.

When is the last spring frost in Middlesex County, Connecticut?

The median last spring freeze runs April 6 – April 26 across the 4 NOAA weather stations serving Middlesex County, Connecticut, from NOAA 1991-2020 Climate Normals. Half of years freeze later than the median.

Connecticut

Planting zones in Middlesex County, Connecticut

This county spans USDA zones 6b to 7a, so there is no single zone for Middlesex County and anyone who gives you one is rounding. 70% of its ZIP codes are zone 6b; the rest are not.

USDA zones 6b–7a 2 zones across 23 ZIP codes

ZIP codes 23 23 have a NOAA station within range

Weather stations 4 NOAA 1991–2020 normals, across 369 sq mi

Your ZIP code

Get the exact answer for your address

Everything above describes Middlesex 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.

Middlesex County does not have one planting answer

Its own weather stations disagree about 14 of the 32 crops in this table right now, so any single list would be wrong for part of the county. That is not a gap in the data — it is what the data says.

Shortest season: 175 days
MERIDEN MARKHAM MUNI AP, CT US (USW00054788)
Longest season: 221 days
ORIENT PT SP, NY US (USC00306276)

46 days of growing season separate those two stations, and both serve ZIP codes in Middlesex County. The ZIP lookup above answers for one address instead of averaging a place that has no average.

Why the hardiness zone does not settle this

A USDA zone is a winter-minimum statistic. It was never a growing-season one, and it does not behave like one: within a single zone the growing season runs a median 54 days wider at the 10th–90th percentile, and annual growing degree days vary by 2.02×.

The zones also overlap rather than stack — 30% of zone 6b freezes before the median zone 6a station. The zone tells you what survives your winter; the station tells you what finishes before your autumn.

The whole dataset behind that →

All 4 stations agreeAt least one station

Every one of the 4 NOAA stations serving this county counts April 26 – October 16 as growing season (173 days). Widening to any single station gives April 6 – November 17 (225 days).

That is a 52-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

Middlesex 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 70% in zone 6b and wrong for the other 30%. Here is the actual split.

Zone	ZIP codes	Share
6b	16	70%
7a	7	30%

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 6 – April 26

First fall freeze October 16 – November 17

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 175–221 days depending which station you are nearest, as published by NOAA rather than computed from the dates above. Summer highs average 79.1–82.4 °F in June–August. Summer rain over the same months runs 11.0–12.3" across those 3 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 85% 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 82 °F summer afternoon drying the soil faster than a cool one.

Every ZIP code in Middlesex 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
06409	7a	Orient Pt SP, NY	27.9 km
06412	6b	Meriden Markham Muni AP, CT	30.4 km
06413	7a	Orient Pt SP, NY	29.0 km
06414	6b	Hartford Brainard FLD, CT	19.5 km
06416	6b	Hartford Brainard FLD, CT	13.3 km
06417	7a	Orient Pt SP, NY	32.0 km
06419	6b	Meriden Markham Muni AP, CT	25.7 km
06422	6b	Meriden Markham Muni AP, CT	12.8 km
06423	6b	Norwich Public Utility Plt, CT	28.3 km
06424	6b	Hartford Brainard FLD, CT	23.1 km
06426	7a	Orient Pt SP, NY	27.0 km
06438	6b	Meriden Markham Muni AP, CT	27.3 km
06441	6b	Meriden Markham Muni AP, CT	21.0 km
06442	7a	Orient Pt SP, NY	27.6 km
06455	6b	Meriden Markham Muni AP, CT	9.2 km
06456	6b	Hartford Brainard FLD, CT	23.4 km
06457	6b	Meriden Markham Muni AP, CT	14.7 km
06459	6b	Meriden Markham Muni AP, CT	14.5 km
06469	6b	Hartford Brainard FLD, CT	30.5 km
06475	7a	Orient Pt SP, NY	21.4 km
06480	6b	Hartford Brainard FLD, CT	16.1 km
06481	6b	Meriden Markham Muni AP, CT	11.2 km
06498	7a	Orient Pt SP, NY	26.5 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 Middlesex 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	February 9 – March 1	8 wk before
🌶️ Peppers	Start indoors	February 9 – March 1	8 wk before
🥦 Broccoli	Start indoors	February 23 – March 15	6 wk before
🥬 Cabbage	Start indoors	February 23 – March 15	6 wk before
🥬 Collards	Start indoors	February 23 – March 15	6 wk before
🥬 Kale	Start indoors	February 23 – March 15	6 wk before
🥬 Leaf Lettuce	Start indoors	February 23 – March 15	6 wk before
🫛 Peas	Direct sow	February 23 – March 15	6 wk before
🥬 Spinach	Direct sow	February 23 – March 15	6 wk before
🍠 Sweet Potato	Start indoors	February 23 – March 15	6 wk before
🍅 Tomatoes	Start indoors	February 23 – March 15	6 wk before
🥬 Bok Choy	Start indoors	March 2 – March 22	5 wk before
🥬 Kohlrabi	Start indoors	March 2 – March 22	5 wk before
🥬 Swiss Chard	Start indoors	March 2 – March 22	5 wk before
🥬 Arugula	Direct sow	March 9 – March 29	4 wk before
🥬 Baby Salad Greens	Direct sow	March 9 – March 29	4 wk before
🥕 Beets	Direct sow	March 9 – March 29	4 wk before
🧅 Green Onions	Direct sow	March 9 – March 29	4 wk before
🥬 Mustard Greens	Direct sow	March 9 – March 29	4 wk before
🌶️ Okra	Start indoors	March 9 – March 29	4 wk before
🌱 Radishes	Direct sow	March 9 – March 29	4 wk before
🥔 Turnips	Direct sow	March 9 – March 29	4 wk before
🥬 Cabbage	Set out	March 16 – April 5	3 wk before
🥕 Carrots	Direct sow	March 16 – April 5	3 wk before
🥬 Collards	Direct sow	March 16 – April 5	3 wk before
🥬 Collards	Set out	March 16 – April 5	3 wk before
🥒 Cucumbers	Start indoors	March 16 – April 5	3 wk before
🧅 Green Onions	Set out	March 16 – April 5	3 wk before
🥬 Kale	Direct sow	March 16 – April 5	3 wk before
🥬 Kale	Set out	March 16 – April 5	3 wk before
🥬 Kohlrabi	Direct sow	March 16 – April 5	3 wk before
🥬 Kohlrabi	Set out	March 16 – April 5	3 wk before
🥬 Leaf Lettuce	Direct sow	March 16 – April 5	3 wk before
🎃 Pumpkins	Start indoors	March 16 – April 5	3 wk before
🎃 Summer Squash	Start indoors	March 16 – April 5	3 wk before
🎃 Winter Squash	Start indoors	March 16 – April 5	3 wk before
🥒 Zucchini	Start indoors	March 16 – April 5	3 wk before
🥬 Bok Choy	Direct sow	March 23 – April 12	2 wk before
🥬 Bok Choy	Set out	March 23 – April 12	2 wk before
🥦 Broccoli	Set out	March 23 – April 12	2 wk before
🌿 Cilantro	Direct sow	March 23 – April 12	2 wk before
🥬 Leaf Lettuce	Set out	March 23 – April 12	2 wk before
🥬 Swiss Chard	Direct sow	March 23 – April 12	2 wk before
🥬 Swiss Chard	Set out	March 23 – April 12	2 wk before
🌿 Dill	Direct sow	March 30 – April 19	1 wk before
🫘 Bush Beans	Direct sow	April 13 – May 3	1 wk after
🥒 Cucumbers	Set out	April 13 – May 3	1 wk after
🎃 Pumpkins	Direct sow	April 13 – May 3	1 wk after
🎃 Pumpkins	Set out	April 13 – May 3	1 wk after
🎃 Summer Squash	Direct sow	April 13 – May 3	1 wk after
🎃 Summer Squash	Set out	April 13 – May 3	1 wk after
🌽 Sweet Corn	Direct sow	April 13 – May 3	1 wk after
🍅 Tomatoes	Set out	April 13 – May 3	1 wk after
🎃 Winter Squash	Direct sow	April 13 – May 3	1 wk after
🎃 Winter Squash	Set out	April 13 – May 3	1 wk after
🥒 Zucchini	Direct sow	April 13 – May 3	1 wk after
🥒 Zucchini	Set out	April 13 – May 3	1 wk after
🥒 Cucumbers	Direct sow	April 20 – May 10	2 wk after
🌶️ Okra	Direct sow	April 20 – May 10	2 wk after
🌶️ Okra	Set out	April 20 – May 10	2 wk after
🌶️ Peppers	Set out	April 20 – May 10	2 wk after
🫘 Southern Peas	Direct sow	April 20 – May 10	2 wk after
🍠 Sweet Potato	Set out	April 20 – May 10	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 Middlesex 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 9 to be careful. Median April 6 – April 26 across 4 stations; March 25 is the optimistic end.
First fall freeze: Plan to October 4 to be careful. Median October 16 – November 17 across 4 stations; December 4 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 67 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
Hartford Brainard FLD, CT	USW00014752	April 17	October 26	191 days
Meriden Markham Muni AP, CT	USW00054788	April 26	October 16	175 days
Norwich Public Utility Plt, CT	USC00065910	April 14	October 24	192 days
Orient Pt SP, NY	USC00306276	April 6	November 17	221 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

Middlesex 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.