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

Planting zone for 56679 — South International Falls, MN

ZIP code 56679 (South International Falls, Koochiching County) is in USDA zone 3b: the coldest winter night averages −35 to −30 °F. The median last spring frost is May 29 and the first fall frost September 13.

Where ZIP 56679 is

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 29
First frostSep 13
2012 zone3a

Was 3a 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 3b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for South International Falls, 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 South International Falls, MN

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 29median — 50% chance of a later frost
Safe for tender plantsJune 16only 10% chance of frost after
First fall frostSeptember 13median — 10% chance by Aug 30
Growing season109 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 14 and returns around September 26.

From the NOAA station Intl Falls Intl Airport, MN — 2 miles away, elevation 1,184 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 56679

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 17 – May 1
SpinachSow outdoors · Apr 17 – May 8
Broccoli, cabbageStart indoors · Mar 20 – Apr 3
Broccoli, cabbageTransplant · May 8 – May 22
Onion setsPlant outdoors · May 1 – May 15
PotatoesPlant outdoors · May 8 – May 22
LettuceSow outdoors · May 1 – May 15
Carrots, beetsSow outdoors · May 8 – May 22
TomatoesStart indoors · Apr 3 – Apr 17
TomatoesTransplant · Jun 5 – Jun 19
Peppers, eggplantStart indoors · Mar 20 – Apr 3
Peppers, eggplantTransplant · Jun 12 – Jun 26
BeansSow outdoors · Jun 5 – Jun 19
Sweet cornSow outdoors · Jun 5 – Jun 19
Cucumbers, squashSow outdoors · Jun 5 – Jun 19
Fall lettuce, spinachSow outdoors · Jul 19 – Aug 2
GarlicPlant cloves · Aug 30 – Oct 4
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 29) and first fall frost (Sep 13) 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 56679 came on May 9 — 10 days later than the 1991–2020 average (Apr 29).

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.

Trees 33

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 °Fbalsam fir60 ft · blooms mid summer · low shade tolerance · to −43 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fbigtooth aspen65 ft · blooms mid spring · high shade tolerance · to −43 °F

Shrubs 50

Allegheny 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 mountain ash40 ft · blooms early summer · medium shade tolerance · to −38 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fbeaked hazelnut15 ft · blooms early spring · low shade tolerance · to −47 °F

Wildflowers & perennials 102

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican speedwell0.8 ft · blooms mid summer · low shade tolerance · to −38 °FAmerican vetch1.3 ft · blooms late spring · high shade tolerance · to −38 °F

Grasses 93

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

Vines 2

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °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 South International Falls, MN.

Soil in South International Falls, MN

The soil mapped at the center of ZIP 56679 is Kooch — silt loam, somewhat poorly drained. Much of the area is built over (urban land); this is the natural soil underneath.

TextureSilt loama good balance for most vegetables
pH6.3slightly acidic; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter5%high
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Urban land-Kooch-Kab complex, 0 to 4 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 56679; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in South International Falls, MN

Summer high78 °Faverage high, July
Winter low−6 °Faverage low, January
Hot days2days a year at 90 °F or more
Freezing nights200nights a year at 32 °F or less
Growing degree days1,543base 50 °F — the season’s usable heat
Longest day16 h 08 mindaylight on June 21
Shortest day8 h 17 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation25.4 inper year, rain and melted snow
Snowfall73 inper year; 136 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 -6 °F 16°−6° JanFebruary: average high 22 °F, low -3 °F 22°−3° FebMarch: average high 35 °F, low 12 °F 35°12° MarApril: average high 50 °F, low 26 °F 50°26° AprMay: average high 64 °F, low 38 °F 64°38° MayJune: average high 74 °F, low 48 °F 74°48° JunJuly: average high 78 °F, low 52 °F 78°52° JulAugust: average high 76 °F, low 50 °F 76°50° AugSeptember: average high 66 °F, low 42 °F 66°42° SepOctober: average high 51 °F, low 31 °F 51°31° OctNovember: average high 34 °F, low 18 °F 34°18° NovDecember: average high 21 °F, low 3 °F 21°3° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″January: 0.79 in precipitation, 15.7 in snowfall 0.8❄16 JanFebruary: 0.69 in precipitation, 12.6 in snowfall 0.7❄13 FebMarch: 1.02 in precipitation, 7.9 in snowfall 1.0❄8 MarApril: 1.64 in precipitation, 7 in snowfall 1.6❄7 AprMay: 3.06 in precipitation, 0.2 in snowfall 3.1 MayJune: 3.78 in precipitation 3.8 JunJuly: 3.97 in precipitation 4.0 JulAugust: 2.82 in precipitation 2.8 AugSeptember: 3.00 in precipitation, 0.1 in snowfall 3.0 SepOctober: 2.22 in precipitation, 1.6 in snowfall 2.2❄2 OctNovember: 1.39 in precipitation, 12.1 in snowfall 1.4❄12 NovDecember: 0.99 in precipitation, 15.8 in snowfall 1.0❄16 Dec

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

Nearby ZIP codes

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

566683a
Ranier, MN · 3 mi
566493b
International Falls, MN · 11 mi
566693b
Kabetogama, MN · 17 mi
566533b
Littlefork, MN · 22 mi
566543a
Loman, MN · 28 mi
566293b
Birchdale, MN · 35 mi
557723b
Nett Lake, MN · 36 mi
557713b
Orr, MN · 40 mi

Minnesota planting zones →

Questions about 56679

What planting zone is ZIP code 56679?

ZIP code 56679 (South International Falls, 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 South International Falls, MN?

The median last spring frost (32 °F) near 56679 is May 29; after June 16 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Intl Falls Intl Airport station.

When is the first frost in South International Falls, MN?

The median first fall frost near 56679 is September 13, giving a median frost-free growing season of 109 days.

When should I plant tomatoes in 56679?

Start tomato seeds indoors around Apr 3 – Apr 17 and set transplants outside around Jun 5 – Jun 19, one to three weeks after the median last frost.

How much rain and snow does 56679 get?

About 25.4 inches of precipitation a year and 73 inches of snowfall (NOAA 1991–2020 normals, Intl Falls Intl Airport station).

How hot do summers get in South International Falls, MN?

The average high peaks at 78 °F in July, with about 2 days a year at 90 °F or more.

What kind of soil does 56679 have?

The USDA soil survey maps Kooch at the center of ZIP 56679: silt loam, somewhat poorly drained, pH about 6.3 (slightly acidic).

Did spring come early in South International Falls, MN in 2026?

Spring leaf-out near 56679 came on May 9 in 2026, 10 days later than the 1991–2020 average (Apr 29), according to the USA National Phenology Network Spring Index.

What kind of onions grow in South International Falls, MN?

Long-day onions: the longest day near 56679 is 16 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 56679 change?

Yes. The 2012 USDA map put 56679 in zone 3a; the 2023 map puts it in zone 3b. The newer map uses 1991–2020 data and more weather stations.