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

Planting zone for 04079 — Harpswell, ME

ZIP code 04079 (Harpswell, Cumberland County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 2 and the first fall frost October 10.

Where ZIP 04079 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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostMay 2
First frostOct 10
2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Harpswell, ME…

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 Harpswell, ME

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 2median — 50% chance of a later frost
Safe for tender plantsMay 14only 10% chance of frost after
First fall frostOctober 10median — 10% chance by Sep 29
Growing season160 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 23.

From the NOAA station Brunswick NAS, ME — 8 miles away, elevation 69 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 04079

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 21 – Apr 4
SpinachSow outdoors · Mar 21 – Apr 11
Broccoli, cabbageStart indoors · Feb 21 – Mar 7
Broccoli, cabbageTransplant · Apr 11 – Apr 25
Onion setsPlant outdoors · Apr 4 – Apr 18
PotatoesPlant outdoors · Apr 11 – Apr 25
LettuceSow outdoors · Apr 4 – Apr 18
Carrots, beetsSow outdoors · Apr 11 – Apr 25
TomatoesStart indoors · Mar 7 – Mar 21
TomatoesTransplant · May 9 – May 23
Peppers, eggplantStart indoors · Feb 21 – Mar 7
Peppers, eggplantTransplant · May 16 – May 30
BeansSow outdoors · May 9 – May 23
Sweet cornSow outdoors · May 9 – May 23
Cucumbers, squashSow outdoors · May 9 – May 23
Fall lettuce, spinachSow outdoors · Aug 15 – Aug 29
GarlicPlant cloves · Sep 26 – Oct 31
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 2) and first fall frost (Oct 10) 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 04079 came on Apr 17 — about the same time as the 1991–2020 average (Apr 19).

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 6a in Maine

502 plants native to the lower 48 states, recorded in Maine, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

Trees 55

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 101

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falpine bearberry0.5 ft · blooms early spring · medium shade tolerance · to −62 °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 °F

Wildflowers & perennials 173

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °F

Grasses 154

alpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °FAmerican beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBailey's sedge2.1 ft · blooms late spring · low shade tolerance · to −33 °F

Vines 6

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °Ftrumpet honeysuckle16 ft · blooms late summer · low shade tolerance · to −33 °FVirginia creeper1 ft · blooms late spring · medium shade tolerance · to −28 °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 Harpswell, ME.

Soil in Harpswell, ME

The soil mapped at the center of ZIP 04079 is Lyman — moderately decomposed plant material, somewhat excessively drained.

TextureModerately decomposed plant materialtop layer
pH3.5strongly acidic; most vegetables like 6.0–7.0
DrainageSomewhat excessively drainednatural drainage class
Organic matter85%high
Hydrologic groupDwater soaks in very slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Lyman loam, 3 to 8 percent slopes, rocky.

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 04079; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Harpswell, ME

Summer high79 °Faverage high, July
Winter low12 °Faverage low, January
Hot days4days a year at 90 °F or more
Freezing nights151nights a year at 32 °F or less
Growing degree days2,120base 50 °F — the season’s usable heat
Longest day15 h 28 mindaylight on June 21
Shortest day8 h 55 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation50 inper year, rain and melted snow
Snowfall67 inper year; 65 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 30 °F, low 12 °F 30°12° JanFebruary: average high 33 °F, low 14 °F 33°14° FebMarch: average high 41 °F, low 24 °F 41°24° MarApril: average high 53 °F, low 32 °F 53°32° AprMay: average high 64 °F, low 44 °F 64°44° MayJune: average high 73 °F, low 53 °F 73°53° JunJuly: average high 79 °F, low 59 °F 79°59° JulAugust: average high 78 °F, low 58 °F 78°58° AugSeptember: average high 70 °F, low 50 °F 70°50° SepOctober: average high 58 °F, low 39 °F 58°39° OctNovember: average high 47 °F, low 30 °F 47°30° NovDecember: average high 37 °F, low 20 °F 37°20° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 3.46 in precipitation, 19.3 in snowfall 3.5❄19 JanFebruary: 3.50 in precipitation, 13.6 in snowfall 3.5❄14 FebMarch: 4.06 in precipitation, 18.7 in snowfall 4.1❄19 MarApril: 4.28 in precipitation, 3.3 in snowfall 4.3❄3 AprMay: 4.06 in precipitation 4.1 MayJune: 4.21 in precipitation 4.2 JunJuly: 3.48 in precipitation 3.5 JulAugust: 3.27 in precipitation 3.3 AugSeptember: 4.20 in precipitation 4.2 SepOctober: 6.00 in precipitation, 0.2 in snowfall 6.0 OctNovember: 5.19 in precipitation, 1.9 in snowfall 5.2❄2 NovDecember: 4.30 in precipitation, 9.8 in snowfall 4.3❄10 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Brunswick NAS, ME (8 mi away); precipitation: Brunswick NAS, ME (8 mi away). 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.

040666a
Orrs Island, ME · 2 mi
040036a
Bailey Island, ME · 4 mi
045656a
Sebasco Estates, ME · 6 mi
040176a
Chebeague Island, ME · 6 mi
040326a
Freeport, ME · 7 mi
040786a
South Freeport, ME · 7 mi
040115b
Brunswick, ME · 7 mi
040336a
Freeport, ME · 8 mi

Maine planting zones →

Questions about 04079

What planting zone is ZIP code 04079?

ZIP code 04079 (Harpswell, ME) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Harpswell, ME?

The median last spring frost (32 °F) near 04079 is May 2; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Brunswick NAS station.

When is the first frost in Harpswell, ME?

The median first fall frost near 04079 is October 10, giving a median frost-free growing season of 160 days.

When should I plant tomatoes in 04079?

Start tomato seeds indoors around Mar 7 – Mar 21 and set transplants outside around May 9 – May 23, one to three weeks after the median last frost.

How much rain and snow does 04079 get?

About 50 inches of precipitation a year and 67 inches of snowfall (NOAA 1991–2020 normals, Brunswick NAS station).

How hot do summers get in Harpswell, ME?

The average high peaks at 79 °F in July, with about 4 days a year at 90 °F or more.

What kind of soil does 04079 have?

The USDA soil survey maps Lyman at the center of ZIP 04079: moderately decomposed plant material, somewhat excessively drained, pH about 3.5 (strongly acidic).

Did spring come early in Harpswell, ME in 2026?

Spring leaf-out near 04079 came on Apr 17 in 2026, about the same as the 1991–2020 average (Apr 19), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Harpswell, ME?

Long-day onions: the longest day near 04079 is 15 h 28 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 04079 change?

Yes. The 2012 USDA map put 04079 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.