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

Planting zone for 06376 — South Lyme, CT

ZIP code 06376 (South Lyme, Lower Connecticut River Valley County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 16 and the first fall frost October 28.

Where ZIP 06376 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.

Zone7a0 to 5 °F
Coldest night−17.8 to −15 °C
Last frostApr 16
First frostOct 28
2012 zone6b

Was 6b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for South Lyme, 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 South Lyme, CT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 16median — 50% chance of a later frost
Safe for tender plantsApril 30only 10% chance of frost after
First fall frostOctober 28median — 10% chance by Oct 13
Growing season194 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 3 and returns around November 9.

From the NOAA station Groton New London Airport, CT — 11 miles away, elevation 10 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 06376

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 5 – Mar 19
SpinachSow outdoors · Mar 5 – Mar 26
Broccoli, cabbageStart indoors · Feb 5 – Feb 19
Broccoli, cabbageTransplant · Mar 26 – Apr 9
Onion setsPlant outdoors · Mar 19 – Apr 2
PotatoesPlant outdoors · Mar 26 – Apr 9
LettuceSow outdoors · Mar 19 – Apr 2
Carrots, beetsSow outdoors · Mar 26 – Apr 9
TomatoesStart indoors · Feb 19 – Mar 5
TomatoesTransplant · Apr 23 – May 7
Peppers, eggplantStart indoors · Feb 5 – Feb 19
Peppers, eggplantTransplant · Apr 30 – May 14
BeansSow outdoors · Apr 23 – May 7
Sweet cornSow outdoors · Apr 23 – May 7
Cucumbers, squashSow outdoors · Apr 23 – May 7
Fall lettuce, spinachSow outdoors · Sep 2 – Sep 16
GarlicPlant cloves · Oct 14 – Nov 18
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 16) and first fall frost (Oct 28) 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 06376 came on Apr 3 — about the same time as the 1991–2020 average (Apr 3).

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 7a in Connecticut

546 plants native to the lower 48 states, recorded in Connecticut, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. Each links to its USDA PLANTS profile.

Trees 65

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 106

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °F

Wildflowers & perennials 191

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °F

Grasses 157

American beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °FAtlantic mannagrass3 ft · blooms summer · low shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °Fbeaked spikerush3 ft · blooms late spring · high shade tolerance · to −28 °F

Vines 10

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °FAmerican wisteria50 ft · blooms spring · low shade tolerance · to −3 °Fcatbird grape30 ft · blooms late spring · medium shade tolerance · to −13 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Fheartleaf peppervine2 ft · blooms late spring · low shade tolerance · to −8 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °F

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 South Lyme, CT.

Soil in South Lyme, CT

The soil mapped at the center of ZIP 06376 is Hollis — highly decomposed plant material, somewhat excessively drained.

TextureHighly decomposed plant materialtop layer
DrainageSomewhat excessively drainednatural drainage class
Organic matter40%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Hollis-Chatfield-Rock outcrop complex, 3 to 15 percent slopes.

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 06376; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in South Lyme, CT

Summer high80 °Faverage high, July
Winter low23 °Faverage low, January
Hot days2days a year at 90 °F or more
Freezing nights107nights a year at 32 °F or less
Growing degree days2,786base 50 °F — the season’s usable heat
Longest day15 h 10 mindaylight on June 21
Shortest day9 h 11 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation47.8 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 38 °F, low 23 °F 38°23° JanFebruary: average high 40 °F, low 25 °F 40°25° FebMarch: average high 47 °F, low 31 °F 47°31° MarApril: average high 56 °F, low 39 °F 56°39° AprMay: average high 65 °F, low 49 °F 65°49° MayJune: average high 74 °F, low 58 °F 74°58° JunJuly: average high 80 °F, low 65 °F 80°65° JulAugust: average high 79 °F, low 64 °F 79°64° AugSeptember: average high 74 °F, low 57 °F 74°57° SepOctober: average high 63 °F, low 46 °F 63°46° OctNovember: average high 53 °F, low 37 °F 53°37° NovDecember: average high 44 °F, low 29 °F 44°29° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.51 in precipitation 3.5 JanFebruary: 3.19 in precipitation 3.2 FebMarch: 4.23 in precipitation 4.2 MarApril: 4.01 in precipitation 4.0 AprMay: 3.54 in precipitation 3.5 MayJune: 4.01 in precipitation 4.0 JunJuly: 3.29 in precipitation 3.3 JulAugust: 4.13 in precipitation 4.1 AugSeptember: 4.45 in precipitation 4.5 SepOctober: 5.05 in precipitation 5.0 OctNovember: 3.83 in precipitation 3.8 NovDecember: 4.58 in precipitation 4.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Groton New London Airport, CT (11 mi away); precipitation: Old Lyme 3.4 Ese, CT (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

063577a
Niantic, CT · 2 mi
063717a
Old Lyme, CT · 6 mi
063337a
East Lyme, CT · 6 mi
064757a
Old Saybrook, CT · 7 mi
063857a
Waterford, CT · 7 mi
064267a
Essex, CT · 8 mi
063207a
New London, CT · 9 mi
119577b
Orient, NY · 9 mi

Connecticut planting zones →

Questions about 06376

What planting zone is ZIP code 06376?

ZIP code 06376 (South Lyme, CT) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in South Lyme, CT?

The median last spring frost (32 °F) near 06376 is April 16; after April 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Groton New London Airport station.

When is the first frost in South Lyme, CT?

The median first fall frost near 06376 is October 28, giving a median frost-free growing season of 194 days.

When should I plant tomatoes in 06376?

Start tomato seeds indoors around Feb 19 – Mar 5 and set transplants outside around Apr 23 – May 7, one to three weeks after the median last frost.

How much rain and snow does 06376 get?

About 47.8 inches of precipitation a year (NOAA 1991–2020 normals, Old Lyme 3.4 Ese station).

How hot do summers get in South Lyme, CT?

The average high peaks at 80 °F in July, with about 2 days a year at 90 °F or more.

What kind of soil does 06376 have?

The USDA soil survey maps Hollis at the center of ZIP 06376: highly decomposed plant material, somewhat excessively drained.

Did spring come early in South Lyme, CT in 2026?

Spring leaf-out near 06376 came on Apr 3 in 2026, about the same as the 1991–2020 average (Apr 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in South Lyme, CT?

Long-day onions: the longest day near 06376 is 15 h 10 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 06376 change?

Yes. The 2012 USDA map put 06376 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.