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

Planting zone for South Portland, ME

South Portland, ME is in USDA zone 6a across its 2 ZIP codes. The median last spring frost is April 26 and the first fall frost October 15.

South Portland on the zone map

Outlined: its 1 ZIP code areas · 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
ZIP codes2
Last frostApr 26
First frostOct 15
Growing season170 days

6a 2 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

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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 South Portland, ME

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 26median — 50% chance of a later frost
Safe for tender plantsMay 7only 10% chance of frost after
First fall frostOctober 15median — 10% chance by Oct 2
Growing season170 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 14 and returns around October 27.

From the NOAA station Portland Intl Jetport, ME, elevation 46 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 South Portland

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 15 – Mar 29
SpinachSow outdoors · Mar 15 – Apr 5
Broccoli, cabbageStart indoors · Feb 15 – Mar 1
Broccoli, cabbageTransplant · Apr 5 – Apr 19
Onion setsPlant outdoors · Mar 29 – Apr 12
PotatoesPlant outdoors · Apr 5 – Apr 19
LettuceSow outdoors · Mar 29 – Apr 12
Carrots, beetsSow outdoors · Apr 5 – Apr 19
TomatoesStart indoors · Mar 1 – Mar 15
TomatoesTransplant · May 3 – May 17
Peppers, eggplantStart indoors · Feb 15 – Mar 1
Peppers, eggplantTransplant · May 10 – May 24
BeansSow outdoors · May 3 – May 17
Sweet cornSow outdoors · May 3 – May 17
Cucumbers, squashSow outdoors · May 3 – May 17
Fall lettuce, spinachSow outdoors · Aug 20 – Sep 3
GarlicPlant cloves · Oct 1 – Nov 5
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 26) and first fall frost (Oct 15) 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 04116 came on Apr 16 — about the same time as the 1991–2020 average (Apr 17).

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 South Portland, ME.

Soil in South Portland, ME

The soil mapped at the center of ZIP 04116 is Deerfield — loamy fine sand, moderately well drained.

TextureLoamy fine sanddrains and warms fast; dries out and needs more feeding
pH5.1strongly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupAwater soaks in fast
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Deerfield loamy fine sand, 3 to 8 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 04116; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in South Portland, ME

Summer high80 °Faverage high, July
Winter low16 °Faverage low, January
Hot days5days a year at 90 °F or more
Freezing nights144nights a year at 32 °F or less
Growing degree days2,327base 50 °F — the season’s usable heat
Longest day15 h 26 mindaylight on June 21
Shortest day8 h 56 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation48.1 inper year, rain and melted snow
Snowfall69 inper year; 74 days with snow on the ground

Average high and low, by month

10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 32 °F, low 16 °F 32°16° JanFebruary: average high 35 °F, low 17 °F 35°17° FebMarch: average high 42 °F, low 26 °F 42°26° MarApril: average high 54 °F, low 35 °F 54°35° AprMay: average high 64 °F, low 46 °F 64°46° MayJune: average high 74 °F, low 55 °F 74°55° JunJuly: average high 80 °F, low 61 °F 80°61° JulAugust: average high 79 °F, low 60 °F 79°60° AugSeptember: average high 71 °F, low 52 °F 71°52° SepOctober: average high 60 °F, low 41 °F 60°41° OctNovember: average high 48 °F, low 32 °F 48°32° NovDecember: average high 38 °F, low 22 °F 38°22° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 3.50 in precipitation, 18.6 in snowfall 3.5❄19 JanFebruary: 3.54 in precipitation, 16.6 in snowfall 3.5❄17 FebMarch: 4.08 in precipitation, 13.6 in snowfall 4.1❄14 MarApril: 4.41 in precipitation, 2.8 in snowfall 4.4❄3 AprMay: 3.67 in precipitation 3.7 MayJune: 4.15 in precipitation 4.2 JunJuly: 3.43 in precipitation 3.4 JulAugust: 3.57 in precipitation 3.6 AugSeptember: 3.77 in precipitation 3.8 SepOctober: 5.25 in precipitation, 0.2 in snowfall 5.3 OctNovember: 4.25 in precipitation, 2.3 in snowfall 4.3❄2 NovDecember: 4.50 in precipitation, 14.6 in snowfall 4.5❄15 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Portland Intl Jetport, ME (3 mi away); precipitation: Portland Intl Jetport, ME (3 mi away). Daylight is calculated from latitude.

ZIP codes in South Portland

041066a
−10 to −5 °F
041166a
−10 to −5 °F

Maine planting zones →

Questions about South Portland

What planting zone is South Portland, ME?

South Portland, ME is in USDA hardiness zone 6a on the 2023 map (6a: −10 to −5 °F).

When is the last frost in South Portland, ME?

The median last spring frost is April 26 and the median first fall frost is October 15 (NOAA 1991–2020 normals, Portland Intl Jetport station).

When can I plant a garden in South Portland, ME?

Cool-season crops like peas and spinach go in around Mar 15 – Apr 5; tomatoes, peppers, beans and squash after about May 3, once frost risk has passed.

What kind of onions grow in South Portland, ME?

Long-day onions: the longest day is 15 h 26 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

How much rain and snow does South Portland, ME get?

About 48.1 inches of precipitation a year and 69 inches of snowfall (NOAA 1991–2020 normals).