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

Planting zone for 55605 — Grand Portage, MN

ZIP code 55605 (Grand Portage, Cook County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 24 and the first fall frost September 29.

Where ZIP 55605 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.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
Last frostMay 24
First frostSep 29
2012 zone4a

Was 4a 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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Grand Portage, MN…

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 Grand Portage, MN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 24median — 50% chance of a later frost
Safe for tender plantsJune 5only 10% chance of frost after
First fall frostSeptember 29median — 10% chance by Sep 16
Growing season127 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 9 and returns around October 9.

From the NOAA station Grand Portage, MN — 2 miles away, elevation 732 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 55605

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 12 – Apr 26
SpinachSow outdoors · Apr 12 – May 3
Broccoli, cabbageStart indoors · Mar 15 – Mar 29
Broccoli, cabbageTransplant · May 3 – May 17
Onion setsPlant outdoors · Apr 26 – May 10
PotatoesPlant outdoors · May 3 – May 17
LettuceSow outdoors · Apr 26 – May 10
Carrots, beetsSow outdoors · May 3 – May 17
TomatoesStart indoors · Mar 29 – Apr 12
TomatoesTransplant · May 31 – Jun 14
Peppers, eggplantStart indoors · Mar 15 – Mar 29
Peppers, eggplantTransplant · Jun 7 – Jun 21
BeansSow outdoors · May 31 – Jun 14
Sweet cornSow outdoors · May 31 – Jun 14
Cucumbers, squashSow outdoors · May 31 – Jun 14
Fall lettuce, spinachSow outdoors · Aug 4 – Aug 18
GarlicPlant cloves · Sep 15 – Oct 20
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 24) and first fall frost (Sep 29) 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 55605 came on May 10 — about the same time as the 1991–2020 average (May 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).

Native plants for zone 4b in Minnesota

497 plants native to the lower 48 states, recorded in Minnesota, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

Trees 47

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °Fbalsam fir60 ft · blooms mid summer · low shade tolerance · to −43 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °F

Shrubs 88

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °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 °FAmerican hornbeam30 ft · blooms mid spring · low shade tolerance · to −34 °F

Wildflowers & perennials 190

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °F

Grasses 156

alkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °FAmerican beachgrass2.5 ft · blooms spring · high shade tolerance · to −28 °Farctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °Fbasin wildrye5 ft · blooms early spring · high shade tolerance · to −43 °Fbeaked sedge4 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 4

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 °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 Grand Portage, MN.

Soil in Grand Portage, MN

The USDA soil survey has no mapped soil at the center of this ZIP code (water, or an area not yet surveyed).

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 55605; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Grand Portage, MN

Summer high74 °Faverage high, July
Winter low1 °Faverage low, January
Hot days1days a year at 90 °F or more
Freezing nights196nights a year at 32 °F or less
Growing degree days1,256base 50 °F — the season’s usable heat
Longest day16 h 02 mindaylight on June 21
Shortest day8 h 22 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation30.6 inper year, rain and melted snow
Snowfall55 inper year; 131 days with snow on the ground

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°32 °FJanuary: average high 20 °F, low 1 °F 20°1° JanFebruary: average high 24 °F, low 2 °F 24°2° FebMarch: average high 34 °F, low 13 °F 34°13° MarApril: average high 45 °F, low 26 °F 45°26° AprMay: average high 58 °F, low 37 °F 58°37° MayJune: average high 68 °F, low 46 °F 68°46° JunJuly: average high 74 °F, low 52 °F 74°52° JulAugust: average high 73 °F, low 52 °F 73°52° AugSeptember: average high 65 °F, low 44 °F 65°44° SepOctober: average high 51 °F, low 33 °F 51°33° OctNovember: average high 38 °F, low 22 °F 38°22° NovDecember: average high 26 °F, low 9 °F 26°9° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″January: 1.35 in precipitation, 12.2 in snowfall 1.4❄12 JanFebruary: 1.03 in precipitation, 8 in snowfall 1.0❄8 FebMarch: 1.33 in precipitation, 8 in snowfall 1.3❄8 MarApril: 2.79 in precipitation, 7.7 in snowfall 2.8❄8 AprMay: 3.11 in precipitation, 0.2 in snowfall 3.1 MayJune: 3.58 in precipitation 3.6 JunJuly: 3.42 in precipitation 3.4 JulAugust: 3.04 in precipitation 3.0 AugSeptember: 3.13 in precipitation 3.1 SepOctober: 3.40 in precipitation, 0.5 in snowfall 3.4❄1 OctNovember: 2.65 in precipitation, 6.7 in snowfall 2.6❄7 NovDecember: 1.74 in precipitation, 11.9 in snowfall 1.7❄12 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Grand Portage, MN (2 mi away); precipitation: Grand Portage, MN (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

556064a
Hovland, MN · 16 mi
556043b
Grand Marais, MN · 44 mi
556123b
Lutsen, MN · 50 mi
499315b
Houghton, MI · 71 mi
499305b
Hancock, MI · 72 mi
499055b
Atlantic Mine, MI · 73 mi
499215b
Dodgeville, MI · 78 mi
499655a
Toivola, MI · 78 mi

Minnesota planting zones →

Questions about 55605

What planting zone is ZIP code 55605?

ZIP code 55605 (Grand Portage, MN) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Grand Portage, MN?

The median last spring frost (32 °F) near 55605 is May 24; after June 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Grand Portage station.

When is the first frost in Grand Portage, MN?

The median first fall frost near 55605 is September 29, giving a median frost-free growing season of 127 days.

When should I plant tomatoes in 55605?

Start tomato seeds indoors around Mar 29 – Apr 12 and set transplants outside around May 31 – Jun 14, one to three weeks after the median last frost.

How much rain and snow does 55605 get?

About 30.6 inches of precipitation a year and 55 inches of snowfall (NOAA 1991–2020 normals, Grand Portage station).

How hot do summers get in Grand Portage, MN?

The average high peaks at 74 °F in July, with about 1 days a year at 90 °F or more.

Did spring come early in Grand Portage, MN in 2026?

Spring leaf-out near 55605 came on May 10 in 2026, about the same as the 1991–2020 average (May 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Grand Portage, MN?

Long-day onions: the longest day near 55605 is 16 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 55605 change?

Yes. The 2012 USDA map put 55605 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.