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

Planting zone for 56540 — Fertile, MN

ZIP code 56540 (Fertile, Polk County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 11 and the first fall frost September 27.

Where ZIP 56540 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 11

First frostSep 27

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 Fertile, 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 Fertile, MN

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 11median — 50% chance of a later frost

Safe for tender plantsMay 25only 10% chance of frost after

First fall frostSeptember 27median — 10% chance by Sep 14

Growing season137 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 6.

From the NOAA station Ada, MN — 20 miles away, elevation 909 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 56540

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 30 – Apr 13

SpinachSow outdoors · Mar 30 – Apr 20

Broccoli, cabbageStart indoors · Mar 2 – Mar 16

Broccoli, cabbageTransplant · Apr 20 – May 4

Onion setsPlant outdoors · Apr 13 – Apr 27

PotatoesPlant outdoors · Apr 20 – May 4

LettuceSow outdoors · Apr 13 – Apr 27

Carrots, beetsSow outdoors · Apr 20 – May 4

TomatoesStart indoors · Mar 16 – Mar 30

TomatoesTransplant · May 18 – Jun 1

Peppers, eggplantStart indoors · Mar 2 – Mar 16

Peppers, eggplantTransplant · May 25 – Jun 8

BeansSow outdoors · May 18 – Jun 1

Sweet cornSow outdoors · May 18 – Jun 1

Cucumbers, squashSow outdoors · May 18 – Jun 1

Fall lettuce, spinachSow outdoors · Aug 2 – Aug 16

GarlicPlant cloves · Sep 13 – Oct 18

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 11) and first fall frost (Sep 27) 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 56540 came on Apr 25 — about the same time as the 1991–2020 average (Apr 24).

average
Apr 242026
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).

Soil in Fertile, MN

The soil mapped at the center of ZIP 56540 is Radium — loamy sand, moderately well drained.

TextureLoamy sanddrains and warms fast; dries out and needs more feeding

pH7.0neutral; most vegetables like 6.0–7.0

DrainageModerately well drainednatural drainage class

Organic matter2%moderate

Hydrologic groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Radium loamy sand, 0 to 2 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 56540; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fertile, MN

Summer high81 °Faverage high, July

Winter low−4 °Faverage low, January

Hot days8days a year at 90 °F or more

Freezing nights180nights a year at 32 °F or less

Growing degree days2,111base 50 °F — the season’s usable heat

Longest day15 h 59 mindaylight on June 21

Shortest day8 h 26 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation24.3 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: Ada, MN (20 mi away); precipitation: Erskine 7.6 Sw, MN (7 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.

Crookston, MN · 19 mi

567503b

Red Lake Falls, MN · 24 mi

Minnesota planting zones →

Questions about 56540

What planting zone is ZIP code 56540?

ZIP code 56540 (Fertile, 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 Fertile, MN?

The median last spring frost (32 °F) near 56540 is May 11; after May 25 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ada station.

When is the first frost in Fertile, MN?

The median first fall frost near 56540 is September 27, giving a median frost-free growing season of 137 days.

When should I plant tomatoes in 56540?

Start tomato seeds indoors around Mar 16 – Mar 30 and set transplants outside around May 18 – Jun 1, one to three weeks after the median last frost.

How much rain and snow does 56540 get?

About 24.3 inches of precipitation a year (NOAA 1991–2020 normals, Erskine 7.6 Sw station).

How hot do summers get in Fertile, MN?

The average high peaks at 81 °F in July, with about 8 days a year at 90 °F or more.

What kind of soil does 56540 have?

The USDA soil survey maps Radium at the center of ZIP 56540: loamy sand, moderately well drained, pH about 7.0 (neutral).

Did spring come early in Fertile, MN in 2026?

Spring leaf-out near 56540 came on Apr 25 in 2026, about the same as the 1991–2020 average (Apr 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fertile, MN?

Long-day onions: the longest day near 56540 is 15 h 59 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 56540 change?

Yes. The 2012 USDA map put 56540 in zone 3b; the 2023 map puts it in zone 4a. The newer map uses 1991–2020 data and more weather stations.