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

Planting zone for 06239 — Danielson, CT

ZIP code 06239 (Danielson, Northeastern Connecticut 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 19.

Where ZIP 06239 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 19
2012 zone6a

Was 6a 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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Danielson, 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 Danielson, 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 9only 10% chance of frost after
First fall frostOctober 19median — 10% chance by Oct 4
Growing season176 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 12 and returns around October 30.

From the NOAA station N Foster 1 E, RI — 7 miles away, elevation 630 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 06239

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 24 – Sep 7
GarlicPlant cloves · Oct 5 – Nov 9
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 25) and first fall frost (Oct 19) 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 06239 came on Apr 3 — 5 days earlier than the 1991–2020 average (Apr 8).

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).

Soil in Danielson, CT

The soil mapped at the center of ZIP 06239 is Woodbridge — moderately decomposed plant material, moderately well drained.

TextureModerately decomposed plant materialtop layer
DrainageModerately well drainednatural drainage class
Organic matter95%high
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Woodbridge fine sandy loam, 3 to 15 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 06239; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Danielson, CT

Summer high80 °Faverage high, July
Winter low19 °Faverage low, January
Hot days4days a year at 90 °F or more
Freezing nights133nights a year at 32 °F or less
Growing degree days2,556base 50 °F — the season’s usable heat
Longest day15 h 13 mindaylight on June 21
Shortest day9 h 08 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation52.2 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 35 °F, low 19 °F 35°19° JanFebruary: average high 38 °F, low 20 °F 38°20° FebMarch: average high 46 °F, low 27 °F 46°27° MarApril: average high 58 °F, low 37 °F 58°37° AprMay: average high 68 °F, low 47 °F 68°47° MayJune: average high 76 °F, low 56 °F 76°56° JunJuly: average high 80 °F, low 61 °F 80°61° JulAugust: average high 79 °F, low 60 °F 79°60° AugSeptember: average high 72 °F, low 53 °F 72°53° SepOctober: average high 61 °F, low 42 °F 61°42° OctNovember: average high 50 °F, low 33 °F 50°33° NovDecember: average high 40 °F, low 24 °F 40°24° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 4.20 in precipitation 4.2 JanFebruary: 3.45 in precipitation 3.5 FebMarch: 4.58 in precipitation 4.6 MarApril: 4.54 in precipitation 4.5 AprMay: 3.64 in precipitation 3.6 MayJune: 4.09 in precipitation 4.1 JunJuly: 3.90 in precipitation 3.9 JulAugust: 5.96 in precipitation 6.0 AugSeptember: 4.24 in precipitation 4.2 SepOctober: 4.82 in precipitation 4.8 OctNovember: 4.03 in precipitation 4.0 NovDecember: 4.78 in precipitation 4.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: N Foster 1 E, RI (7 mi away); precipitation: East Killingly 1.3 Sw, CT (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

062636b
Rogers, CT · 4 mi
062416b
Dayville, CT · 4 mi
062436b
East Killingly, CT · 4 mi
063876b
Wauregan, CT · 4 mi
063776b
Sterling, CT · 5 mi
062346b
Brooklyn, CT · 5 mi
063326b
Central Village, CT · 6 mi
062336b
Ballouville, CT · 6 mi

Connecticut planting zones →

Questions about 06239

What planting zone is ZIP code 06239?

ZIP code 06239 (Danielson, 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 Danielson, CT?

The median last spring frost (32 °F) near 06239 is April 25; after May 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, N Foster 1 E station.

When is the first frost in Danielson, CT?

The median first fall frost near 06239 is October 19, giving a median frost-free growing season of 176 days.

When should I plant tomatoes in 06239?

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 06239 get?

About 52.2 inches of precipitation a year (NOAA 1991–2020 normals, East Killingly 1.3 Sw station).

How hot do summers get in Danielson, CT?

The average high peaks at 80 °F in July, with about 4 days a year at 90 °F or more.

What kind of soil does 06239 have?

The USDA soil survey maps Woodbridge at the center of ZIP 06239: moderately decomposed plant material, moderately well drained.

Did spring come early in Danielson, CT in 2026?

Spring leaf-out near 06239 came on Apr 3 in 2026, 5 days earlier than the 1991–2020 average (Apr 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Danielson, CT?

Long-day onions: the longest day near 06239 is 15 h 13 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 06239 change?

Yes. The 2012 USDA map put 06239 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.