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

Planting zone for 04645 — Isle Au Haut, ME

ZIP code 04645 (Isle Au Haut, Knox County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 27 and the first fall frost October 19.

Where ZIP 04645 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 27
First frostOct 19
2012 zone5b

Was 5b on the 2012 map — a full 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 Isle Au Haut, 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 Isle Au Haut, ME

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 27median — 50% chance of a later frost
Safe for tender plantsMay 9only 10% chance of frost after
First fall frostOctober 19median — 10% chance by Oct 5
Growing season175 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 15 and returns around October 31.

From the NOAA station W Rockport 1 Nnw, ME — 27 miles away, elevation 361 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 04645

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 16 – Mar 30
SpinachSow outdoors · Mar 16 – Apr 6
Broccoli, cabbageStart indoors · Feb 16 – Mar 2
Broccoli, cabbageTransplant · Apr 6 – Apr 20
Onion setsPlant outdoors · Mar 30 – Apr 13
PotatoesPlant outdoors · Apr 6 – Apr 20
LettuceSow outdoors · Mar 30 – Apr 13
Carrots, beetsSow outdoors · Apr 6 – Apr 20
TomatoesStart indoors · Mar 2 – Mar 16
TomatoesTransplant · May 4 – May 18
Peppers, eggplantStart indoors · Feb 16 – Mar 2
Peppers, eggplantTransplant · May 11 – May 25
BeansSow outdoors · May 4 – May 18
Sweet cornSow outdoors · May 4 – May 18
Cucumbers, squashSow outdoors · May 4 – May 18
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 27) 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 04645 came on Apr 16 — 8 days earlier than the 1991–2020 average (Apr 24).

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 Maine

506 plants native to the lower 48 states, recorded in Maine, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. 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 175

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 156

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 °FAtlantic mannagrass3 ft · blooms summer · low shade tolerance · to −8 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °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 Isle Au Haut, ME.

Soil in Isle Au Haut, ME

The soil mapped at the center of ZIP 04645 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 classNot prime farmlandUSDA classification

Map unit: Rock outcrop-Lyman complex, 3 to 15 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 04645; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Isle Au Haut, ME

Summer high77 °Faverage high, July
Winter low12 °Faverage low, January
Hot days2days a year at 90 °F or more
Freezing nights148nights a year at 32 °F or less
Growing degree days2,043base 50 °F — the season’s usable heat
Longest day15 h 30 mindaylight on June 21
Shortest day8 h 53 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation56.2 inper year, rain and melted snow
Snowfall69 inper year

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 40 °F, low 22 °F 40°22° MarApril: average high 51 °F, low 34 °F 51°34° AprMay: average high 62 °F, low 44 °F 62°44° MayJune: average high 71 °F, low 54 °F 71°54° JunJuly: average high 77 °F, low 60 °F 77°60° JulAugust: average high 76 °F, low 59 °F 76°59° AugSeptember: average high 69 °F, low 52 °F 69°52° SepOctober: average high 57 °F, low 41 °F 57°41° OctNovember: average high 47 °F, low 31 °F 47°31° NovDecember: average high 36 °F, low 20 °F 36°20° Dec

Precipitation by month inches · ❄ = snowfall

0″2″4″6″January: 4.75 in precipitation, 17.2 in snowfall 4.8❄17 JanFebruary: 4.20 in precipitation, 19.2 in snowfall 4.2❄19 FebMarch: 5.01 in precipitation, 11.3 in snowfall 5.0❄11 MarApril: 5.21 in precipitation, 3.5 in snowfall 5.2❄4 AprMay: 4.22 in precipitation 4.2 MayJune: 4.49 in precipitation 4.5 JunJuly: 3.20 in precipitation 3.2 JulAugust: 3.37 in precipitation 3.4 AugSeptember: 4.49 in precipitation 4.5 SepOctober: 6.07 in precipitation, 0.2 in snowfall 6.1 OctNovember: 5.27 in precipitation, 2.3 in snowfall 5.3❄2 NovDecember: 5.92 in precipitation, 15 in snowfall 5.9❄15 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: W Rockport 1 Nnw, ME (27 mi away); precipitation: W Rockport 1 Nnw, ME (27 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

5 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

046816a
Stonington, ME · 6 mi
046856b
Swans Island, ME · 11 mi
048636b
Vinalhaven, ME · 12 mi
048536a
North Haven, ME · 13 mi
046356b
Frenchboro, ME · 13 mi
046276a
Deer Isle, ME · 14 mi
046166a
Brooklin, ME · 15 mi
046836a
Sunset, ME · 16 mi

Maine planting zones →

Questions about 04645

What planting zone is ZIP code 04645?

ZIP code 04645 (Isle Au Haut, ME) 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 Isle Au Haut, ME?

The median last spring frost (32 °F) near 04645 is April 27; after May 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, W Rockport 1 Nnw station.

When is the first frost in Isle Au Haut, ME?

The median first fall frost near 04645 is October 19, giving a median frost-free growing season of 175 days.

When should I plant tomatoes in 04645?

Start tomato seeds indoors around Mar 2 – Mar 16 and set transplants outside around May 4 – May 18, one to three weeks after the median last frost.

How much rain and snow does 04645 get?

About 56.2 inches of precipitation a year and 69 inches of snowfall (NOAA 1991–2020 normals, W Rockport 1 Nnw station).

How hot do summers get in Isle Au Haut, ME?

The average high peaks at 77 °F in July, with about 2 days a year at 90 °F or more.

What kind of soil does 04645 have?

The USDA soil survey maps Lyman at the center of ZIP 04645: moderately decomposed plant material, somewhat excessively drained, pH about 3.5 (strongly acidic).

Did spring come early in Isle Au Haut, ME in 2026?

Spring leaf-out near 04645 came on Apr 16 in 2026, 8 days earlier than the 1991–2020 average (Apr 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Isle Au Haut, ME?

Long-day onions: the longest day near 04645 is 15 h 30 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 04645 change?

Yes. The 2012 USDA map put 04645 in zone 5b; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.