Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 55604 — Grand Marais, MN

ZIP code 55604 (Grand Marais, Cook County) is in USDA zone 3b: the coldest winter night averages −35 to −30 °F. The median last spring frost is May 23 and the first fall frost September 26.

Where ZIP 55604 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.

Zone3b−35 to −30 °F

Coldest night−37.2 to −34.4 °C

Last frostMay 23

First frostSep 26

2012 zone4a

Was 4a on the 2012 map — half a zone colder now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 3b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Grand Marais, 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 Marais, MN

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 23median — 50% chance of a later frost

Safe for tender plantsJune 7only 10% chance of frost after

First fall frostSeptember 26median — 10% chance by Sep 11

Growing season124 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 11 and returns around October 7.

From the NOAA station Gunflint Lake 10 Nw, MN — 18 miles away, elevation 1,457 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 55604

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 11 – Apr 25

SpinachSow outdoors · Apr 11 – May 2

Broccoli, cabbageStart indoors · Mar 14 – Mar 28

Broccoli, cabbageTransplant · May 2 – May 16

Onion setsPlant outdoors · Apr 25 – May 9

PotatoesPlant outdoors · May 2 – May 16

LettuceSow outdoors · Apr 25 – May 9

Carrots, beetsSow outdoors · May 2 – May 16

TomatoesStart indoors · Mar 28 – Apr 11

TomatoesTransplant · May 30 – Jun 13

Peppers, eggplantStart indoors · Mar 14 – Mar 28

Peppers, eggplantTransplant · Jun 6 – Jun 20

BeansSow outdoors · May 30 – Jun 13

Sweet cornSow outdoors · May 30 – Jun 13

Cucumbers, squashSow outdoors · May 30 – Jun 13

Fall lettuce, spinachSow outdoors · Aug 1 – Aug 15

GarlicPlant cloves · Sep 12 – Oct 17

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 23) and first fall frost (Sep 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 55604 came on May 9 — 5 days later than the 1991–2020 average (May 4).

average
May 42026
May 9

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 3b in Minnesota

287 plants native to the lower 48 states, recorded in Minnesota, and rated by the USDA to survive −35 °F or colder — the bottom of zone 3b. Each links to its USDA PLANTS profile.

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 Marais, MN.

Soil in Grand Marais, MN

The soil mapped at the center of ZIP 55604 is Eveleth — stony loam, well drained.

TextureStony loama good balance for most vegetables

pH4.9strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter5%high

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Eveleth, bouldery-Conic, bouldery-Rock outcrop complex, 18 to 35 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 55604; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Grand Marais, MN

Summer high76 °Faverage high, July

Winter low−6 °Faverage low, January

Hot days3days a year at 90 °F or more

Freezing nights200nights a year at 32 °F or less

Growing degree days1,513base 50 °F — the season’s usable heat

Longest day16 h 03 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)

Precipitation29.2 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Gunflint Lake 10 Nw, MN (18 mi away); precipitation: Grand Marais 4.4 W, MN (17 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.

Schroeder, MN · 33 mi

556034a

Finland, MN · 41 mi

556054b

Grand Portage, MN · 44 mi

556073b

Isabella, MN · 49 mi

556144a

Silver Bay, MN · 57 mi

Minnesota planting zones →

Questions about 55604

What planting zone is ZIP code 55604?

ZIP code 55604 (Grand Marais, MN) is in USDA hardiness zone 3b on the 2023 map: the coldest night of an average winter reaches −35 to −30 °F (−37.2 to −34.4 °C).

When is the last frost in Grand Marais, MN?

The median last spring frost (32 °F) near 55604 is May 23; after June 7 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Gunflint Lake 10 Nw station.

When is the first frost in Grand Marais, MN?

The median first fall frost near 55604 is September 26, giving a median frost-free growing season of 124 days.

When should I plant tomatoes in 55604?

Start tomato seeds indoors around Mar 28 – Apr 11 and set transplants outside around May 30 – Jun 13, one to three weeks after the median last frost.

How much rain and snow does 55604 get?

About 29.2 inches of precipitation a year (NOAA 1991–2020 normals, Grand Marais 4.4 W station).

How hot do summers get in Grand Marais, MN?

The average high peaks at 76 °F in July, with about 3 days a year at 90 °F or more.

What kind of soil does 55604 have?

The USDA soil survey maps Eveleth at the center of ZIP 55604: stony loam, well drained, pH about 4.9 (strongly acidic).

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

Spring leaf-out near 55604 came on May 9 in 2026, 5 days later than the 1991–2020 average (May 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Grand Marais, MN?

Long-day onions: the longest day near 55604 is 16 h 03 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 55604 change?

Yes. The 2012 USDA map put 55604 in zone 4a; the 2023 map puts it in zone 3b. The newer map uses 1991–2020 data and more weather stations.