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

Planting zone for 06416 — Cromwell, CT

ZIP code 06416 (Cromwell, Lower Connecticut River Valley County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 17 and the first fall frost October 26.

Where ZIP 06416 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 17
First frostOct 26
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 Cromwell, 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 Cromwell, CT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 17median — 50% chance of a later frost
Safe for tender plantsMay 1only 10% chance of frost after
First fall frostOctober 26median — 10% chance by Oct 12
Growing season191 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 3 and returns around November 5.

From the NOAA station Hartford Brainard Field, CT — 8 miles away, elevation 20 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 06416

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 6 – Mar 20
SpinachSow outdoors · Mar 6 – Mar 27
Broccoli, cabbageStart indoors · Feb 6 – Feb 20
Broccoli, cabbageTransplant · Mar 27 – Apr 10
Onion setsPlant outdoors · Mar 20 – Apr 3
PotatoesPlant outdoors · Mar 27 – Apr 10
LettuceSow outdoors · Mar 20 – Apr 3
Carrots, beetsSow outdoors · Mar 27 – Apr 10
TomatoesStart indoors · Feb 20 – Mar 6
TomatoesTransplant · Apr 24 – May 8
Peppers, eggplantStart indoors · Feb 6 – Feb 20
Peppers, eggplantTransplant · May 1 – May 15
BeansSow outdoors · Apr 24 – May 8
Sweet cornSow outdoors · Apr 24 – May 8
Cucumbers, squashSow outdoors · Apr 24 – May 8
Fall lettuce, spinachSow outdoors · Aug 31 – Sep 14
GarlicPlant cloves · Oct 12 – Nov 16
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 17) and first fall frost (Oct 26) 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 06416 came on Apr 1 — 4 days earlier than the 1991–2020 average (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.

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 Cromwell, CT.

Soil in Cromwell, CT

The soil mapped at the center of ZIP 06416 is Walpole — mucky peat, poorly drained.

TextureMucky peattop layer
DrainagePoorly drainedconsider raised beds
Organic matter80%high
Hydrologic groupB/Dmoderate when drained; wet otherwise
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Walpole sandy loam, 0 to 3 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 06416; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cromwell, CT

Summer high85 °Faverage high, July
Winter low20 °Faverage low, January
Hot days17days a year at 90 °F or more
Freezing nights121nights a year at 32 °F or less
Growing degree days3,238base 50 °F — the season’s usable heat
Longest day15 h 12 mindaylight on June 21
Shortest day9 h 09 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation48.8 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 37 °F, low 20 °F 37°20° JanFebruary: average high 40 °F, low 22 °F 40°22° FebMarch: average high 48 °F, low 30 °F 48°30° MarApril: average high 60 °F, low 40 °F 60°40° AprMay: average high 71 °F, low 50 °F 71°50° MayJune: average high 80 °F, low 60 °F 80°60° JunJuly: average high 85 °F, low 66 °F 85°66° JulAugust: average high 83 °F, low 64 °F 83°64° AugSeptember: average high 76 °F, low 56 °F 76°56° SepOctober: average high 64 °F, low 44 °F 64°44° OctNovember: average high 52 °F, low 35 °F 52°35° NovDecember: average high 42 °F, low 26 °F 42°26° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 3.63 in precipitation 3.6 JanFebruary: 3.02 in precipitation 3.0 FebMarch: 3.97 in precipitation 4.0 MarApril: 4.40 in precipitation 4.4 AprMay: 3.65 in precipitation 3.6 MayJune: 4.41 in precipitation 4.4 JunJuly: 3.89 in precipitation 3.9 JulAugust: 3.97 in precipitation 4.0 AugSeptember: 4.27 in precipitation 4.3 SepOctober: 5.18 in precipitation 5.2 OctNovember: 3.72 in precipitation 3.7 NovDecember: 4.72 in precipitation 4.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Hartford Brainard Field, CT (8 mi away); precipitation: Rocky Hill 1.3 E, CT (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

060676b
Rocky Hill, CT · 3 mi
060236b
East Berlin, CT · 3 mi
064806b
Portland, CT · 4 mi
064596b
Middletown, CT · 5 mi
064576b
Middletown, CT · 5 mi
060736b
South Glastonbury, CT · 6 mi
064816b
Rockfall, CT · 6 mi
061096b
Wethersfield, CT · 6 mi

Connecticut planting zones →

Questions about 06416

What planting zone is ZIP code 06416?

ZIP code 06416 (Cromwell, 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 Cromwell, CT?

The median last spring frost (32 °F) near 06416 is April 17; after May 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hartford Brainard Field station.

When is the first frost in Cromwell, CT?

The median first fall frost near 06416 is October 26, giving a median frost-free growing season of 191 days.

When should I plant tomatoes in 06416?

Start tomato seeds indoors around Feb 20 – Mar 6 and set transplants outside around Apr 24 – May 8, one to three weeks after the median last frost.

How much rain and snow does 06416 get?

About 48.8 inches of precipitation a year (NOAA 1991–2020 normals, Rocky Hill 1.3 E station).

How hot do summers get in Cromwell, CT?

The average high peaks at 85 °F in July, with about 17 days a year at 90 °F or more.

What kind of soil does 06416 have?

The USDA soil survey maps Walpole at the center of ZIP 06416: mucky peat, poorly drained.

Did spring come early in Cromwell, CT in 2026?

Spring leaf-out near 06416 came on Apr 1 in 2026, 4 days earlier than the 1991–2020 average (Apr 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cromwell, CT?

Long-day onions: the longest day near 06416 is 15 h 12 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).