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

Planting zone for 52639 — Montrose, IA

ZIP code 52639 (Montrose, Lee County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 17 and the first fall frost October 22.

Where ZIP 52639 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.

Zone6a−10 to −5 °F

Coldest night−23.3 to −20.6 °C

Last frostApr 17

First frostOct 22

2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Montrose, IA…

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 Montrose, IA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 17median — 50% chance of a later frost

Safe for tender plantsMay 1only 10% chance of frost after

First fall frostOctober 22median — 10% chance by Oct 10

Growing season187 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 7 and returns around November 1.

From the NOAA station Donnellson, IA — 9 miles away, elevation 705 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 52639

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 6 – Mar 20

SpinachSow outdoors · Mar 6 – Mar 27

Broccoli, cabbageStart indoors · Feb 6 – Feb 20

Broccoli, cabbageTransplant · Mar 27 – Apr 10

Onion setsPlant outdoors · Mar 20 – Apr 3

PotatoesPlant outdoors · Mar 27 – Apr 10

LettuceSow outdoors · Mar 20 – Apr 3

Carrots, beetsSow outdoors · Mar 27 – Apr 10

TomatoesStart indoors · Feb 20 – Mar 6

TomatoesTransplant · Apr 24 – May 8

Peppers, eggplantStart indoors · Feb 6 – Feb 20

Peppers, eggplantTransplant · May 1 – May 15

BeansSow outdoors · Apr 24 – May 8

Sweet cornSow outdoors · Apr 24 – May 8

Cucumbers, squashSow outdoors · Apr 24 – May 8

Fall lettuce, spinachSow outdoors · Aug 27 – Sep 10

GarlicPlant cloves · Oct 8 – Nov 12

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 17) and first fall frost (Oct 22) 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 52639 came on Mar 11 — 16 days earlier than the 1991–2020 average (Mar 27).

average
Mar 272026
Mar 11

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 Montrose, IA

The soil mapped at the center of ZIP 52639 is Ashgrove — silty clay loam, poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up

pH5.9moderately acidic; most vegetables like 6.0–7.0

DrainagePoorly drainedconsider raised beds

Organic matter1.7%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Ashgrove soils, 5 to 9 percent slopes, severely eroded.

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 52639; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Montrose, IA

Summer high86 °Faverage high, July

Winter low15 °Faverage low, January

Hot days30days a year at 90 °F or more

Freezing nights129nights a year at 32 °F or less

Growing degree days3,540base 50 °F — the season’s usable heat

Longest day15 h 04 mindaylight on June 21

Shortest day9 h 16 mindaylight on December 21

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

Precipitation39.2 inper year, rain and melted snow

Snowfall27 inper year; 40 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Donnellson, IA (9 mi away); precipitation: Donnellson, IA (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 6a.

Donnellson, IA · 10 mi

634726a

Wayland, MO · 10 mi

634306a

Alexandria, MO · 10 mi

634656a

Revere, MO · 11 mi

526276a

Fort Madison, IA · 11 mi

Iowa planting zones →

Questions about 52639

What planting zone is ZIP code 52639?

ZIP code 52639 (Montrose, IA) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Montrose, IA?

The median last spring frost (32 °F) near 52639 is April 17; after May 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Donnellson station.

When is the first frost in Montrose, IA?

The median first fall frost near 52639 is October 22, giving a median frost-free growing season of 187 days.

When should I plant tomatoes in 52639?

Start tomato seeds indoors around Feb 20 – Mar 6 and set transplants outside around Apr 24 – May 8, one to three weeks after the median last frost.

How much rain and snow does 52639 get?

About 39.2 inches of precipitation a year and 27 inches of snowfall (NOAA 1991–2020 normals, Donnellson station).

How hot do summers get in Montrose, IA?

The average high peaks at 86 °F in July, with about 30 days a year at 90 °F or more.

What kind of soil does 52639 have?

The USDA soil survey maps Ashgrove at the center of ZIP 52639: silty clay loam, poorly drained, pH about 5.9 (moderately acidic).

Did spring come early in Montrose, IA in 2026?

Spring leaf-out near 52639 came on Mar 11 in 2026, 16 days earlier than the 1991–2020 average (Mar 27), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Montrose, IA?

Long-day onions: the longest day near 52639 is 15 h 04 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 52639 change?

Yes. The 2012 USDA map put 52639 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.