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

Planting zone for 06480 — Portland, CT

ZIP code 06480 (Portland, 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 06480 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 Portland, 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 Portland, 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 — 10 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 06480

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 06480 came on Apr 1 — 5 days earlier than the 1991–2020 average (Apr 6).

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 Portland, CT

The soil mapped at the center of ZIP 06480 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 06480; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Portland, 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 (10 mi away); precipitation: Rocky Hill 1.3 E, CT (5 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6b.

064146b
Cobalt, CT · 2 mi
064166b
Cromwell, CT · 4 mi
060736b
South Glastonbury, CT · 4 mi
064566b
Middle Haddam, CT · 5 mi
064596b
Middletown, CT · 5 mi
064576b
Middletown, CT · 5 mi
064246b
East Hampton, CT · 5 mi
060676b
Rocky Hill, CT · 5 mi

Connecticut planting zones →

Questions about 06480

What planting zone is ZIP code 06480?

ZIP code 06480 (Portland, 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 Portland, CT?

The median last spring frost (32 °F) near 06480 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 Portland, CT?

The median first fall frost near 06480 is October 26, giving a median frost-free growing season of 191 days.

When should I plant tomatoes in 06480?

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 06480 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 Portland, 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 06480 have?

The USDA soil survey maps Ridgebury at the center of ZIP 06480: moderately decomposed plant material, poorly drained.

Did spring come early in Portland, CT in 2026?

Spring leaf-out near 06480 came on Apr 1 in 2026, 5 days earlier than the 1991–2020 average (Apr 6), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Portland, CT?

Long-day onions: the longest day near 06480 is 15 h 12 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).