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

Planting zone for 55609 — Knife River, MN

ZIP code 55609 (Knife River, Lake County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 12 and the first fall frost October 6.

Where ZIP 55609 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 12
First frostOct 6
2012 zone4b

Same zone as on the 2012 map. 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 Knife River, 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 Knife River, MN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 12median — 50% chance of a later frost
Safe for tender plantsMay 30only 10% chance of frost after
First fall frostOctober 6median — 10% chance by Sep 19
Growing season145 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 29 and returns around October 20.

From the NOAA station Two Harbors, MN — 7 miles away, elevation 627 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 55609

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 31 – Apr 14
SpinachSow outdoors · Mar 31 – Apr 21
Broccoli, cabbageStart indoors · Mar 3 – Mar 17
Broccoli, cabbageTransplant · Apr 21 – May 5
Onion setsPlant outdoors · Apr 14 – Apr 28
PotatoesPlant outdoors · Apr 21 – May 5
LettuceSow outdoors · Apr 14 – Apr 28
Carrots, beetsSow outdoors · Apr 21 – May 5
TomatoesStart indoors · Mar 17 – Mar 31
TomatoesTransplant · May 19 – Jun 2
Peppers, eggplantStart indoors · Mar 3 – Mar 17
Peppers, eggplantTransplant · May 26 – Jun 9
BeansSow outdoors · May 19 – Jun 2
Sweet cornSow outdoors · May 19 – Jun 2
Cucumbers, squashSow outdoors · May 19 – Jun 2
Fall lettuce, spinachSow outdoors · Aug 11 – Aug 25
GarlicPlant cloves · Sep 22 – Oct 27
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 12) and first fall frost (Oct 6) 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 55609 came on May 3 — 3 days later than the 1991–2020 average (Apr 30).

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 Knife River, MN.

Soil in Knife River, MN

The soil mapped at the center of ZIP 55609 is Cuttre — silt loam, somewhat poorly drained.

TextureSilt loama good balance for most vegetables
pH5.6moderately acidic; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter5%high
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Cuttre-Bergland complex, 0 to 8 percent slopes, very rocky.

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 55609; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Knife River, MN

Summer high75 °Faverage high, July
Winter low7 °Faverage low, January
Hot days1days a year at 90 °F or more
Freezing nights164nights a year at 32 °F or less
Growing degree days1,492base 50 °F — the season’s usable heat
Longest day15 h 53 mindaylight on June 21
Shortest day8 h 31 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation33.1 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 24 °F, low 7 °F 24°7° JanFebruary: average high 28 °F, low 10 °F 28°10° FebMarch: average high 37 °F, low 21 °F 37°21° MarApril: average high 48 °F, low 31 °F 48°31° AprMay: average high 58 °F, low 39 °F 58°39° MayJune: average high 67 °F, low 46 °F 67°46° JunJuly: average high 75 °F, low 55 °F 75°55° JulAugust: average high 75 °F, low 56 °F 75°56° AugSeptember: average high 67 °F, low 49 °F 67°49° SepOctober: average high 54 °F, low 38 °F 54°38° OctNovember: average high 40 °F, low 26 °F 40°26° NovDecember: average high 29 °F, low 14 °F 29°14° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 1.36 in precipitation 1.4 JanFebruary: 1.30 in precipitation 1.3 FebMarch: 1.71 in precipitation 1.7 MarApril: 2.82 in precipitation 2.8 AprMay: 3.36 in precipitation 3.4 MayJune: 4.16 in precipitation 4.2 JunJuly: 4.41 in precipitation 4.4 JulAugust: 3.62 in precipitation 3.6 AugSeptember: 3.50 in precipitation 3.5 SepOctober: 3.24 in precipitation 3.2 OctNovember: 1.69 in precipitation 1.7 NovDecember: 1.91 in precipitation 1.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Two Harbors, MN (7 mi away); precipitation: Two Harbors 3.6 Wnw, MN (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

558044b
Duluth, MN · 7 mi
558034a
Duluth, MN · 14 mi
558124b
Duluth, MN · 17 mi
558054b
Duluth, MN · 18 mi
558154b
Duluth, MN · 20 mi
558165a
Duluth, MN · 20 mi
558025a
Duluth, MN · 20 mi
558064b
Duluth, MN · 21 mi

Minnesota planting zones →

Questions about 55609

What planting zone is ZIP code 55609?

ZIP code 55609 (Knife River, 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 Knife River, MN?

The median last spring frost (32 °F) near 55609 is May 12; after May 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Two Harbors station.

When is the first frost in Knife River, MN?

The median first fall frost near 55609 is October 6, giving a median frost-free growing season of 145 days.

When should I plant tomatoes in 55609?

Start tomato seeds indoors around Mar 17 – Mar 31 and set transplants outside around May 19 – Jun 2, one to three weeks after the median last frost.

How much rain and snow does 55609 get?

About 33.1 inches of precipitation a year (NOAA 1991–2020 normals, Two Harbors 3.6 Wnw station).

How hot do summers get in Knife River, MN?

The average high peaks at 75 °F in July, with about 1 days a year at 90 °F or more.

What kind of soil does 55609 have?

The USDA soil survey maps Cuttre at the center of ZIP 55609: silt loam, somewhat poorly drained, pH about 5.6 (moderately acidic).

Did spring come early in Knife River, MN in 2026?

Spring leaf-out near 55609 came on May 3 in 2026, 3 days later than the 1991–2020 average (Apr 30), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Knife River, MN?

Long-day onions: the longest day near 55609 is 15 h 53 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).