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

Planting zone for 56744 — Oslo, MN

ZIP code 56744 (Oslo, Marshall County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 15 and the first fall frost September 26.

Where ZIP 56744 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 15
First frostSep 26
2012 zone4a

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 4a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Oslo, 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 Oslo, MN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 15median — 50% chance of a later frost
Safe for tender plantsMay 28only 10% chance of frost after
First fall frostSeptember 26median — 10% chance by Sep 13
Growing season134 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 4 and returns around October 6.

From the NOAA station Argyle, MN — 15 miles away, elevation 846 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 56744

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 3 – Apr 17
SpinachSow outdoors · Apr 3 – Apr 24
Broccoli, cabbageStart indoors · Mar 6 – Mar 20
Broccoli, cabbageTransplant · Apr 24 – May 8
Onion setsPlant outdoors · Apr 17 – May 1
PotatoesPlant outdoors · Apr 24 – May 8
LettuceSow outdoors · Apr 17 – May 1
Carrots, beetsSow outdoors · Apr 24 – May 8
TomatoesStart indoors · Mar 20 – Apr 3
TomatoesTransplant · May 22 – Jun 5
Peppers, eggplantStart indoors · Mar 6 – Mar 20
Peppers, eggplantTransplant · May 29 – Jun 12
BeansSow outdoors · May 22 – Jun 5
Sweet cornSow outdoors · May 22 – Jun 5
Cucumbers, squashSow outdoors · May 22 – Jun 5
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 15) 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 56744 came on Apr 27 — about the same time as the 1991–2020 average (Apr 25).

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 Oslo, MN.

Soil in Oslo, MN

The soil mapped at the center of ZIP 56744 is Fargo — silty clay, poorly drained.

TextureSilty clayholds water and nutrients; slow to drain and warm up
pH7.2neutral; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter5%high
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Fargo silty clay, 0 to 1 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 56744; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Oslo, MN

Summer high82 °Faverage high, July
Winter low−5 °Faverage low, January
Hot days9days a year at 90 °F or more
Freezing nights194nights a year at 32 °F or less
Growing degree days2,057base 50 °F — the season’s usable heat
Longest day16 h 05 mindaylight on June 21
Shortest day8 h 20 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation22.9 inper year, rain and melted snow
Snowfall44 inper year; 105 days with snow on the ground

Average high and low, by month

−20°−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 16 °F, low -5 °F 16°−5° JanFebruary: average high 21 °F, low -2 °F 21°−2° FebMarch: average high 35 °F, low 13 °F 35°13° MarApril: average high 53 °F, low 28 °F 53°28° AprMay: average high 68 °F, low 40 °F 68°40° MayJune: average high 77 °F, low 52 °F 77°52° JunJuly: average high 82 °F, low 55 °F 82°55° JulAugust: average high 81 °F, low 53 °F 81°53° AugSeptember: average high 72 °F, low 44 °F 72°44° SepOctober: average high 55 °F, low 32 °F 55°32° OctNovember: average high 36 °F, low 18 °F 36°18° NovDecember: average high 22 °F, low 4 °F 22°4° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″January: 0.68 in precipitation, 9 in snowfall 0.7❄9 JanFebruary: 0.59 in precipitation, 7.2 in snowfall 0.6❄7 FebMarch: 0.87 in precipitation, 6.7 in snowfall 0.9❄7 MarApril: 1.15 in precipitation, 2.7 in snowfall 1.1❄3 AprMay: 3.02 in precipitation, 0.1 in snowfall 3.0 MayJune: 3.96 in precipitation 4.0 JunJuly: 3.04 in precipitation 3.0 JulAugust: 3.02 in precipitation 3.0 AugSeptember: 2.69 in precipitation 2.7 SepOctober: 2.03 in precipitation, 1.5 in snowfall 2.0❄2 OctNovember: 0.97 in precipitation, 5.5 in snowfall 1.0❄6 NovDecember: 0.85 in precipitation, 10.9 in snowfall 0.8❄11 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Argyle, MN (15 mi away); precipitation: Argyle, MN (15 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 4a.

567104a
Alvarado, MN · 6 mi
582614a
Minto, ND · 9 mi
582564a
Manvel, ND · 11 mi
567134a
Argyle, MN · 16 mi
582374a
Grafton, ND · 18 mi
582034a
Grand Forks, ND · 18 mi
582584a
Mekinock, ND · 18 mi
582354a
Gilby, ND · 20 mi

Minnesota planting zones →

Questions about 56744

What planting zone is ZIP code 56744?

ZIP code 56744 (Oslo, 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 Oslo, MN?

The median last spring frost (32 °F) near 56744 is May 15; after May 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Argyle station.

When is the first frost in Oslo, MN?

The median first fall frost near 56744 is September 26, giving a median frost-free growing season of 134 days.

When should I plant tomatoes in 56744?

Start tomato seeds indoors around Mar 20 – Apr 3 and set transplants outside around May 22 – Jun 5, one to three weeks after the median last frost.

How much rain and snow does 56744 get?

About 22.9 inches of precipitation a year and 44 inches of snowfall (NOAA 1991–2020 normals, Argyle station).

How hot do summers get in Oslo, MN?

The average high peaks at 82 °F in July, with about 9 days a year at 90 °F or more.

What kind of soil does 56744 have?

The USDA soil survey maps Fargo at the center of ZIP 56744: silty clay, poorly drained, pH about 7.2 (neutral).

Did spring come early in Oslo, MN in 2026?

Spring leaf-out near 56744 came on Apr 27 in 2026, about the same as the 1991–2020 average (Apr 25), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Oslo, MN?

Long-day onions: the longest day near 56744 is 16 h 05 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).