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

Planting zone for 56736 — Mentor, MN

ZIP code 56736 (Mentor, Polk County) is in USDA zone 4a: the coldest winter night averages −30 to −25 °F. The median last spring frost is May 9 and the first fall frost September 30.

Where ZIP 56736 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 9

First frostSep 30

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 Mentor, 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 Mentor, MN

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 9median — 50% chance of a later frost

Safe for tender plantsMay 24only 10% chance of frost after

First fall frostSeptember 30median — 10% chance by Sep 16

Growing season142 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 30 and returns around October 8.

From the NOAA station Red Lake Falls, MN — 12 miles away, elevation 1,037 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 56736

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 28 – Apr 11

SpinachSow outdoors · Mar 28 – Apr 18

Broccoli, cabbageStart indoors · Feb 28 – Mar 14

Broccoli, cabbageTransplant · Apr 18 – May 2

Onion setsPlant outdoors · Apr 11 – Apr 25

PotatoesPlant outdoors · Apr 18 – May 2

LettuceSow outdoors · Apr 11 – Apr 25

Carrots, beetsSow outdoors · Apr 18 – May 2

TomatoesStart indoors · Mar 14 – Mar 28

TomatoesTransplant · May 16 – May 30

Peppers, eggplantStart indoors · Feb 28 – Mar 14

Peppers, eggplantTransplant · May 23 – Jun 6

BeansSow outdoors · May 16 – May 30

Sweet cornSow outdoors · May 16 – May 30

Cucumbers, squashSow outdoors · May 16 – May 30

Fall lettuce, spinachSow outdoors · Aug 5 – Aug 19

GarlicPlant cloves · Sep 16 – Oct 21

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 9) and first fall frost (Sep 30) 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 56736 came on Apr 25 — about the same time as the 1991–2020 average (Apr 25).

average
Apr 252026
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.

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 Mentor, MN.

Soil in Mentor, MN

The soil mapped at the center of ZIP 56736 is Strathcona — fine sandy loam, poorly drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding

pH7.9alkaline; most vegetables like 6.0–7.0

DrainagePoorly drainedconsider raised beds

Organic matter6%high

Hydrologic groupB/Dmoderate when drained; wet otherwise

Farmland classPrime farmland if drainedUSDA classification

Map unit: Strathcona fine sandy loam, 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 56736; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mentor, MN

Summer high79 °Faverage high, July

Winter low−3 °Faverage low, January

Hot days5days a year at 90 °F or more

Freezing nights182nights a year at 32 °F or less

Growing degree days2,088base 50 °F — the season’s usable heat

Longest day16 h 00 mindaylight on June 21

Shortest day8 h 24 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: Red Lake Falls, MN (12 mi away); precipitation: Erskine 7.6 Sw, MN (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Red Lake Falls, MN · 13 mi

Saint Hilaire, MN · 19 mi

Minnesota planting zones →

Questions about 56736

What planting zone is ZIP code 56736?

ZIP code 56736 (Mentor, 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 Mentor, MN?

The median last spring frost (32 °F) near 56736 is May 9; after May 24 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Red Lake Falls station.

When is the first frost in Mentor, MN?

The median first fall frost near 56736 is September 30, giving a median frost-free growing season of 142 days.

When should I plant tomatoes in 56736?

Start tomato seeds indoors around Mar 14 – Mar 28 and set transplants outside around May 16 – May 30, one to three weeks after the median last frost.

How much rain and snow does 56736 get?

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

How hot do summers get in Mentor, MN?

The average high peaks at 79 °F in July, with about 5 days a year at 90 °F or more.

What kind of soil does 56736 have?

The USDA soil survey maps Strathcona at the center of ZIP 56736: fine sandy loam, poorly drained, pH about 7.9 (alkaline).

Did spring come early in Mentor, MN in 2026?

Spring leaf-out near 56736 came on Apr 25 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 Mentor, MN?

Long-day onions: the longest day near 56736 is 16 h 00 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 56736 change?

Yes. The 2012 USDA map put 56736 in zone 3b; the 2023 map puts it in zone 4a. The newer map uses 1991–2020 data and more weather stations.