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Home Garden Lot: Garden & Home Improvement

What Hardiness Zone Is Connecticut?

USDA 2023 Plant Hardiness Zone Map · 419 ZIP codes · Data updated 2026-10-28

Quick answer

Connecticut spans USDA hardiness zones 6a–7b on the 2023 Plant Hardiness Zone Map. The most common zone is 6b, covering 60% of Connecticut's ZIP codes, followed by zone 7a (27%). Zone 6b means the coldest night of an average winter reaches −5°F to 0°F (−21°C to −18°C). Enter your ZIP code for your exact zone.

Connecticut hardiness zones by share of ZIP codes

Zone 6a12% · 51 ZIPs
Zone 6b60% · 252 ZIPs
Zone 7a27% · 113 ZIPs
Zone 7b<1% · 3 ZIPs

What the zones mean for Connecticut gardeners

  • Coldest and warmest towns: among towns with NOAA weather stations, Norfolk 2 SW (1,340 ft) is in zone 6a, while New Haven Tweed Airport (3 ft) is in zone 7a. That is a difference of about 10°F in the coldest night of a typical winter.
  • Same zone, different frost dates: within zone 6b, the median last spring frost ranges from April 14 at Norwich Public Utility Plt to May 7 at Staffordville, 23 days apart. Your zone tells you which perennials survive winter; your frost dates tell you when to plant.

Typical frost dates in each Connecticut zone

Medians across NOAA weather stations in each zone. Colder zones usually have later spring frosts, but local terrain can shift the dates by weeks.

ZoneLast spring frostFirst fall frostStations
6aMay 3October 115
6bApril 25October 1613
7aApril 16October 285

Hardiness zones for Connecticut cities

Zones at the National Weather Service stations, mostly city airports, with their median frost dates.
Bridgeport Sikorsky Memorial Airport7a0°F to 5°F5Apr 5Nov 6
Danbury Municipal Airport6b−5°F to 0°F457May 1Oct 14
Groton New London Airport7a0°F to 5°F10Apr 16Oct 28
Hartford Bradley Intl Airport6b−5°F to 0°F190Apr 21Oct 16
Hartford Brainard Field6b−5°F to 0°F19Apr 17Oct 26
Meriden Markham Municipal Airport6b−5°F to 0°F103Apr 26Oct 16
New Haven Tweed Airport7a0°F to 5°F3Apr 17Oct 27
Willimantic Windham Airport6b−5°F to 0°F247Apr 28Oct 13

Hardiness zones for 23 towns in Connecticut

Each NOAA weather station is shown with the USDA zone of the nearest ZIP code (within 8 miles). Coldest night is the zone's range for the average annual extreme minimum temperature. Click a column to sort.
Ansonia 1 NE6b−5°F to 0°F136Apr 25Oct 17
Bakersville6a−10°F to −5°F686May 8Oct 5
Barkhamsted6a−10°F to −5°F710Apr 30Oct 17
Bridgeport Sikorsky Memorial Airport7a0°F to 5°F5Apr 5Nov 6
Burlington6a−10°F to −5°F505Apr 25Oct 18
Danbury6b−5°F to 0°F405Apr 20Oct 20
Danbury Municipal Airport6b−5°F to 0°F457May 1Oct 14
Falls Village6a−10°F to −5°F550May 11Oct 4
Groton7a0°F to 5°F40Apr 8Nov 2
Groton New London Airport7a0°F to 5°F10Apr 16Oct 28
Hampton6b−5°F to 0°F490Apr 30Oct 15
Hartford Bradley Intl Airport6b−5°F to 0°F190Apr 21Oct 16
Hartford Brainard Field6b−5°F to 0°F19Apr 17Oct 26
Meriden Markham Municipal Airport6b−5°F to 0°F103Apr 26Oct 16
Mount Carmel6b−5°F to 0°F180Apr 18Oct 26
New Haven Tweed Airport7a0°F to 5°F3Apr 17Oct 27
Norfolk 2 SW6a−10°F to −5°F1,340May 3Oct 11
Norwich Public Utility Plt6b−5°F to 0°F20Apr 14Oct 24
Staffordville6b−5°F to 0°F736May 7Oct 12
Stamford 5 N7a0°F to 5°F190Apr 17Oct 23
Storrs6b−5°F to 0°F665Apr 19Oct 22
W Thompson Lake6b−5°F to 0°F360May 1Oct 9
Willimantic Windham Airport6b−5°F to 0°F247Apr 28Oct 13

Frequently asked questions

What hardiness zone is Connecticut?

Connecticut is in USDA hardiness zones 6a–7b on the 2023 USDA Plant Hardiness Zone Map. Zone 6b is the most common, covering 60% of Connecticut's ZIP codes, and zone 7a covers 27%. Enter your ZIP code for your exact zone.

What does zone 6b mean?

Zone 6b means the average annual extreme minimum temperature, the coldest night of a typical winter, is −5°F to 0°F (−21°C to −18°C). Perennials, shrubs and trees rated for zone 6b or colder should survive winter there.

What is the coldest hardiness zone in Connecticut?

Zone 6a is the coldest zone mapped in Connecticut, found around Norfolk 2 SW, and zone 7b is the warmest.

Did Connecticut's hardiness zones change in 2023?

The USDA released a new Plant Hardiness Zone Map in November 2023, based on 1991–2020 temperatures instead of 1976–2005. About half of the United States shifted half a zone warmer. Check your ZIP code here, because plant tags and older books may still list your 2012 zone.

When should I plant in zone 6b?

Hardiness zones don't set planting dates; frost dates do. Inside zone 6b in Connecticut, the median last spring frost varies from April 14 to May 7. Look up your local frost dates and plant tender crops such as tomatoes after the 10%-risk last-frost date.

Zone and frost dates: use both

Your hardiness zone answers one question: will this plant survive the winter here? Choose perennials, shrubs, trees and bulbs rated for your zone or a colder one. For vegetables and annuals, what matters is the length of the frost-free season. See Connecticut frost dates by town, or get a planting calendar for your ZIP code with start-indoors, transplant and sowing dates for 30 crops.

Sources and method

Zones are from the USDA 2023 Plant Hardiness Zone Map ZIP-code files published by the PRISM Climate Group, Oregon State University, based on 1991–2020 minimum temperatures. ZIP codes are assigned to states by USPS prefix. Town zones use the ZIP code nearest each NOAA 1991–2020 Climate Normals station. This is an independent tool, not an official USDA site. Full methodology.

Hardiness zones in other states