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

Planting zone for 55726 — Cromwell, MN

ZIP code 55726 (Cromwell, Carlton County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 31 and the first fall frost September 18.

Where ZIP 55726 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.

Zone4a−30 to −25 °F
Coldest night−34.4 to −31.7 °C
Last frostMay 31
First frostSep 18
2012 zone3b

Was 3b 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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Cromwell, 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 Cromwell, MN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 31median — 50% chance of a later frost
Safe for tender plantsJune 20only 10% chance of frost after
First fall frostSeptember 18median — 10% chance by Sep 1
Growing season107 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 17 and returns around September 28.

From the NOAA station Wright 3 E, MN — 6 miles away, elevation 1,329 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 55726

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 19 – May 3
SpinachSow outdoors · Apr 19 – May 10
Broccoli, cabbageStart indoors · Mar 22 – Apr 5
Broccoli, cabbageTransplant · May 10 – May 24
Onion setsPlant outdoors · May 3 – May 17
PotatoesPlant outdoors · May 10 – May 24
LettuceSow outdoors · May 3 – May 17
Carrots, beetsSow outdoors · May 10 – May 24
TomatoesStart indoors · Apr 5 – Apr 19
TomatoesTransplant · Jun 7 – Jun 21
Peppers, eggplantStart indoors · Mar 22 – Apr 5
Peppers, eggplantTransplant · Jun 14 – Jun 28
BeansSow outdoors · Jun 7 – Jun 21
Sweet cornSow outdoors · Jun 7 – Jun 21
Cucumbers, squashSow outdoors · Jun 7 – Jun 21
Fall lettuce, spinachSow outdoors · Jul 24 – Aug 7
GarlicPlant cloves · Sep 4 – Oct 9
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 31) and first fall frost (Sep 18) 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 55726 came on Apr 23 — 3 days earlier than the 1991–2020 average (Apr 26).

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 4a in Minnesota

445 plants native to the lower 48 states, recorded in Minnesota, and rated by the USDA to survive −30 °F or colder — the bottom of zone 4a. Each links to its USDA PLANTS profile.

Trees 45

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 77

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 173

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 140

alkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °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 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °F

Vines 3

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 °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 Cromwell, MN.

Soil in Cromwell, MN

The soil mapped at the center of ZIP 55726 is Mooselake — muck, very poorly drained.

TextureMucktop layer
DrainageVery poorly drainedconsider raised beds
Organic matter65%high
Hydrologic groupA/Ddrains fast once dried out; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Mooselake mucky peat.

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 55726; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cromwell, MN

Summer high76 °Faverage high, July
Winter low−3 °Faverage low, January
Hot days1days a year at 90 °F or more
Freezing nights190nights a year at 32 °F or less
Growing degree days1,457base 50 °F — the season’s usable heat
Longest day15 h 51 mindaylight on June 21
Shortest day8 h 33 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation31.2 inper year, rain and melted snow
Snowfall59 inper year; 121 days with snow on the ground

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 18 °F, low -3 °F 18°−3° JanFebruary: average high 24 °F, low 0 °F 24°0° FebMarch: average high 36 °F, low 13 °F 36°13° MarApril: average high 50 °F, low 26 °F 50°26° AprMay: average high 64 °F, low 37 °F 64°37° MayJune: average high 72 °F, low 47 °F 72°47° JunJuly: average high 76 °F, low 52 °F 76°52° JulAugust: average high 75 °F, low 50 °F 75°50° AugSeptember: average high 66 °F, low 43 °F 66°43° SepOctober: average high 52 °F, low 32 °F 52°32° OctNovember: average high 36 °F, low 19 °F 36°19° NovDecember: average high 23 °F, low 5 °F 23°5° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 0.63 in precipitation, 10.6 in snowfall 0.6❄11 JanFebruary: 0.81 in precipitation, 11.9 in snowfall 0.8❄12 FebMarch: 1.48 in precipitation, 8.3 in snowfall 1.5❄8 MarApril: 2.33 in precipitation, 4.7 in snowfall 2.3❄5 AprMay: 3.50 in precipitation, 0.2 in snowfall 3.5 MayJune: 4.72 in precipitation 4.7 JunJuly: 4.36 in precipitation 4.4 JulAugust: 4.13 in precipitation 4.1 AugSeptember: 3.24 in precipitation 3.2 SepOctober: 3.26 in precipitation, 2 in snowfall 3.3❄2 OctNovember: 1.53 in precipitation, 9.2 in snowfall 1.5❄9 NovDecember: 1.17 in precipitation, 12.3 in snowfall 1.2❄12 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Wright 3 E, MN (6 mi away); precipitation: Wright 3 E, MN (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4a.

557804a
Sawyer, MN · 7 mi
557984a
Wright, MN · 8 mi
557574a
Kettle River, MN · 10 mi
557074a
Barnum, MN · 11 mi
557114a
Brookston, MN · 13 mi
557674a
Moose Lake, MN · 14 mi
557874a
Tamarack, MN · 14 mi
557204a
Cloquet, MN · 16 mi

Minnesota planting zones →

Questions about 55726

What planting zone is ZIP code 55726?

ZIP code 55726 (Cromwell, MN) is in USDA hardiness zone 4a on the 2023 map: the coldest night of an average winter reaches −30 to −25 °F (−34.4 to −31.7 °C).

When is the last frost in Cromwell, MN?

The median last spring frost (32 °F) near 55726 is May 31; after June 20 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Wright 3 E station.

When is the first frost in Cromwell, MN?

The median first fall frost near 55726 is September 18, giving a median frost-free growing season of 107 days.

When should I plant tomatoes in 55726?

Start tomato seeds indoors around Apr 5 – Apr 19 and set transplants outside around Jun 7 – Jun 21, one to three weeks after the median last frost.

How much rain and snow does 55726 get?

About 31.2 inches of precipitation a year and 59 inches of snowfall (NOAA 1991–2020 normals, Wright 3 E station).

How hot do summers get in Cromwell, MN?

The average high peaks at 76 °F in July, with about 1 days a year at 90 °F or more.

What kind of soil does 55726 have?

The USDA soil survey maps Mooselake at the center of ZIP 55726: muck, very poorly drained.

Did spring come early in Cromwell, MN in 2026?

Spring leaf-out near 55726 came on Apr 23 in 2026, 3 days earlier than the 1991–2020 average (Apr 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cromwell, MN?

Long-day onions: the longest day near 55726 is 15 h 51 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 55726 change?

Yes. The 2012 USDA map put 55726 in zone 3b; the 2023 map puts it in zone 4a. The newer map uses 1991–2020 data and more weather stations.