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

Planting zone for 06401 — Ansonia, CT

ZIP code 06401 (Ansonia, Naugatuck Valley County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 25 and the first fall frost October 17.

Where ZIP 06401 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 25
First frostOct 17
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 Ansonia, 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 Ansonia, CT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 25median — 50% chance of a later frost
Safe for tender plantsMay 10only 10% chance of frost after
First fall frostOctober 17median — 10% chance by Oct 4
Growing season175 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 10 and returns around October 30.

From the NOAA station Ansonia 1 Ne, CT — within 1 mile, elevation 138 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 06401

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 14 – Mar 28
SpinachSow outdoors · Mar 14 – Apr 4
Broccoli, cabbageStart indoors · Feb 14 – Feb 28
Broccoli, cabbageTransplant · Apr 4 – Apr 18
Onion setsPlant outdoors · Mar 28 – Apr 11
PotatoesPlant outdoors · Apr 4 – Apr 18
LettuceSow outdoors · Mar 28 – Apr 11
Carrots, beetsSow outdoors · Apr 4 – Apr 18
TomatoesStart indoors · Feb 28 – Mar 14
TomatoesTransplant · May 2 – May 16
Peppers, eggplantStart indoors · Feb 14 – Feb 28
Peppers, eggplantTransplant · May 9 – May 23
BeansSow outdoors · May 2 – May 16
Sweet cornSow outdoors · May 2 – May 16
Cucumbers, squashSow outdoors · May 2 – May 16
Fall lettuce, spinachSow outdoors · Aug 22 – Sep 5
GarlicPlant cloves · Oct 3 – Nov 7
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 25) and first fall frost (Oct 17) 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 06401 came on Apr 2 — about the same time as the 1991–2020 average (Apr 4).

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.

Trees 64

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 105

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 187

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 151

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 9

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °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 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °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 Ansonia, CT.

Soil in Ansonia, CT

The soil mapped at the center of ZIP 06401 is Ridgebury — moderately decomposed plant material, poorly drained.

TextureModerately decomposed plant materialtop layer
DrainagePoorly drainedconsider raised beds
Organic matter95%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Ridgebury, Leicester, and Whitman soils, 0 to 8 percent slopes, extremely stony.

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 06401; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ansonia, CT

Summer high82 °Faverage high, July
Winter low18 °Faverage low, January
Hot days10days a year at 90 °F or more
Freezing nights130nights a year at 32 °F or less
Growing degree days2,823base 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)
Precipitation52 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 36 °F, low 18 °F 36°18° JanFebruary: average high 38 °F, low 19 °F 38°19° FebMarch: average high 47 °F, low 27 °F 47°27° MarApril: average high 58 °F, low 38 °F 58°38° AprMay: average high 69 °F, low 47 °F 69°47° MayJune: average high 77 °F, low 58 °F 77°58° JunJuly: average high 82 °F, low 63 °F 82°63° JulAugust: average high 82 °F, low 62 °F 82°62° AugSeptember: average high 75 °F, low 54 °F 75°54° SepOctober: average high 63 °F, low 41 °F 63°41° OctNovember: average high 52 °F, low 32 °F 52°32° NovDecember: average high 41 °F, low 23 °F 41°23° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.95 in precipitation 4.0 JanFebruary: 3.62 in precipitation 3.6 FebMarch: 4.72 in precipitation 4.7 MarApril: 4.72 in precipitation 4.7 AprMay: 4.04 in precipitation 4.0 MayJune: 3.93 in precipitation 3.9 JunJuly: 4.30 in precipitation 4.3 JulAugust: 4.56 in precipitation 4.6 AugSeptember: 4.38 in precipitation 4.4 SepOctober: 5.00 in precipitation 5.0 OctNovember: 4.24 in precipitation 4.2 NovDecember: 4.57 in precipitation 4.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Ansonia 1 Ne, CT (within 1 mile); precipitation: Ansonia 1 Ne, CT (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

064186b
Derby, CT · 1 mi
064836b
Seymour, CT · 3 mi
065256b
New Haven, CT · 4 mi
064846b
Shelton, CT · 5 mi
064777a
Orange, CT · 5 mi
065157a
New Haven, CT · 5 mi
065246b
Bethany, CT · 7 mi
064916b
Stevenson, CT · 7 mi

Connecticut planting zones →

Questions about 06401

What planting zone is ZIP code 06401?

ZIP code 06401 (Ansonia, 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 Ansonia, CT?

The median last spring frost (32 °F) near 06401 is April 25; after May 10 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ansonia 1 Ne station.

When is the first frost in Ansonia, CT?

The median first fall frost near 06401 is October 17, giving a median frost-free growing season of 175 days.

When should I plant tomatoes in 06401?

Start tomato seeds indoors around Feb 28 – Mar 14 and set transplants outside around May 2 – May 16, one to three weeks after the median last frost.

How much rain and snow does 06401 get?

About 52 inches of precipitation a year (NOAA 1991–2020 normals, Ansonia 1 Ne station).

How hot do summers get in Ansonia, CT?

The average high peaks at 82 °F in July, with about 10 days a year at 90 °F or more.

What kind of soil does 06401 have?

The USDA soil survey maps Ridgebury at the center of ZIP 06401: moderately decomposed plant material, poorly drained.

Did spring come early in Ansonia, CT in 2026?

Spring leaf-out near 06401 came on Apr 2 in 2026, about the same as the 1991–2020 average (Apr 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ansonia, CT?

Long-day onions: the longest day near 06401 is 15 h 10 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).