Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 06339 — Ledyard, CT

ZIP code 06339 (Ledyard, Southeastern Connecticut County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 8 and the first fall frost November 2.

Where ZIP 06339 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone6b−5 to 0 °F

Coldest night−20.6 to −17.8 °C

Last frostApr 8

First frostNov 2

2012 zone6b

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Ledyard, CT…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Ledyard, CT

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 8median — 50% chance of a later frost

Safe for tender plantsApril 22only 10% chance of frost after

First fall frostNovember 2median — 10% chance by Oct 18

Growing season207 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 29 and returns around November 14.

From the NOAA station Groton, CT — 7 miles away, elevation 39 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 06339

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 25 – Mar 11

SpinachSow outdoors · Feb 25 – Mar 18

Broccoli, cabbageStart indoors · Jan 28 – Feb 11

Broccoli, cabbageTransplant · Mar 18 – Apr 1

Onion setsPlant outdoors · Mar 11 – Mar 25

PotatoesPlant outdoors · Mar 18 – Apr 1

LettuceSow outdoors · Mar 11 – Mar 25

Carrots, beetsSow outdoors · Mar 18 – Apr 1

TomatoesStart indoors · Feb 11 – Feb 25

TomatoesTransplant · Apr 15 – Apr 29

Peppers, eggplantStart indoors · Jan 28 – Feb 11

Peppers, eggplantTransplant · Apr 22 – May 6

BeansSow outdoors · Apr 15 – Apr 29

Sweet cornSow outdoors · Apr 15 – Apr 29

Cucumbers, squashSow outdoors · Apr 15 – Apr 29

Fall lettuce, spinachSow outdoors · Sep 7 – Sep 21

GarlicPlant cloves · Oct 19 – Nov 23

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 8) and first fall frost (Nov 2) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 06339 came on Apr 5 — about the same time as the 1991–2020 average (Apr 5).

average
Apr 52026
Apr 5

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 6b in Connecticut

533 plants native to the lower 48 states, recorded in Connecticut, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Ledyard, CT.

Soil in Ledyard, CT

The soil mapped at the center of ZIP 06339 is Charlton — moderately decomposed plant material, well drained.

TextureModerately decomposed plant materialtop layer

DrainageWell drainednatural drainage class

Organic matter95%high

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Charlton-Chatfield complex, 0 to 15 percent slopes, very rocky.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 06339; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ledyard, CT

Summer high81 °Faverage high, July

Winter low24 °Faverage low, January

Hot days3days a year at 90 °F or more

Freezing nights102nights a year at 32 °F or less

Growing degree days2,990base 50 °F — the season’s usable heat

Longest day15 h 11 mindaylight on June 21

Shortest day9 h 10 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation48.9 inper year, rain and melted snow

Snowfall25 inper year; 21 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Groton, CT (7 mi away); precipitation: Groton, CT (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

5 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

063386b

Mashantucket, CT · 2 mi

063357a

Gales Ferry, CT · 4 mi

063727a

Old Mystic, CT · 4 mi

Stonington, CT · 6 mi

063596b

North Stonington, CT · 6 mi

063407a

Groton, CT · 7 mi

Connecticut planting zones →

Questions about 06339

What planting zone is ZIP code 06339?

ZIP code 06339 (Ledyard, CT) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Ledyard, CT?

The median last spring frost (32 °F) near 06339 is April 8; after April 22 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Groton station.

When is the first frost in Ledyard, CT?

The median first fall frost near 06339 is November 2, giving a median frost-free growing season of 207 days.

When should I plant tomatoes in 06339?

Start tomato seeds indoors around Feb 11 – Feb 25 and set transplants outside around Apr 15 – Apr 29, one to three weeks after the median last frost.

How much rain and snow does 06339 get?

About 48.9 inches of precipitation a year and 25 inches of snowfall (NOAA 1991–2020 normals, Groton station).

How hot do summers get in Ledyard, CT?

The average high peaks at 81 °F in July, with about 3 days a year at 90 °F or more.

What kind of soil does 06339 have?

The USDA soil survey maps Charlton at the center of ZIP 06339: moderately decomposed plant material, well drained.

Did spring come early in Ledyard, CT in 2026?

Spring leaf-out near 06339 came on Apr 5 in 2026, about the same as the 1991–2020 average (Apr 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ledyard, CT?

Long-day onions: the longest day near 06339 is 15 h 11 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).