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

Planting zone for 52162 — Postville, IA

ZIP code 52162 (Postville, Allamakee County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 1 and the first fall frost October 3.

Where ZIP 52162 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.

Zone5a−20 to −15 °F

Coldest night−28.9 to −26.1 °C

Last frostMay 1

First frostOct 3

2012 zone4b

Was 4b 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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Postville, 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 Postville, IA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 1median — 50% chance of a later frost

Safe for tender plantsMay 14only 10% chance of frost after

First fall frostOctober 3median — 10% chance by Sep 20

Growing season153 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 12.

From the NOAA station Postville, IA — within 1 mile, elevation 1,165 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 52162

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 20 – Apr 3

SpinachSow outdoors · Mar 20 – Apr 10

Broccoli, cabbageStart indoors · Feb 20 – Mar 6

Broccoli, cabbageTransplant · Apr 10 – Apr 24

Onion setsPlant outdoors · Apr 3 – Apr 17

PotatoesPlant outdoors · Apr 10 – Apr 24

LettuceSow outdoors · Apr 3 – Apr 17

Carrots, beetsSow outdoors · Apr 10 – Apr 24

TomatoesStart indoors · Mar 6 – Mar 20

TomatoesTransplant · May 8 – May 22

Peppers, eggplantStart indoors · Feb 20 – Mar 6

Peppers, eggplantTransplant · May 15 – May 29

BeansSow outdoors · May 8 – May 22

Sweet cornSow outdoors · May 8 – May 22

Cucumbers, squashSow outdoors · May 8 – May 22

Fall lettuce, spinachSow outdoors · Aug 8 – Aug 22

GarlicPlant cloves · Sep 19 – Oct 24

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 1) and first fall frost (Oct 3) 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 52162 came on Mar 30 — 14 days earlier than the 1991–2020 average (Apr 13).

average
Apr 132026
Mar 30

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 5a in Iowa

461 plants native to the lower 48 states, recorded in Iowa, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. 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 Postville, IA.

Soil in Postville, IA

The soil mapped at the center of ZIP 52162 is Downs — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH6.2slightly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2.5%moderate

Hydrologic groupCwater soaks in slowly

Farmland classFarmland of statewide importanceUSDA classification

Map unit: Downs silt loam, 9 to 14 percent slopes, moderately 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 52162; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Postville, IA

Summer high83 °Faverage high, July

Winter low7 °Faverage low, January

Hot days9days a year at 90 °F or more

Freezing nights162nights a year at 32 °F or less

Growing degree days2,659base 50 °F — the season’s usable heat

Longest day15 h 23 mindaylight on June 21

Shortest day8 h 59 mindaylight on December 21

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

Precipitation38.9 inper year, rain and melted snow

Snowfall40 inper year; 77 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: Postville, IA (within 1 mile); precipitation: Postville, IA (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

Farmersburg, IA · 14 mi

Iowa planting zones →

Questions about 52162

What planting zone is ZIP code 52162?

ZIP code 52162 (Postville, IA) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Postville, IA?

The median last spring frost (32 °F) near 52162 is May 1; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Postville station.

When is the first frost in Postville, IA?

The median first fall frost near 52162 is October 3, giving a median frost-free growing season of 153 days.

When should I plant tomatoes in 52162?

Start tomato seeds indoors around Mar 6 – Mar 20 and set transplants outside around May 8 – May 22, one to three weeks after the median last frost.

How much rain and snow does 52162 get?

About 38.9 inches of precipitation a year and 40 inches of snowfall (NOAA 1991–2020 normals, Postville station).

How hot do summers get in Postville, IA?

The average high peaks at 83 °F in July, with about 9 days a year at 90 °F or more.

What kind of soil does 52162 have?

The USDA soil survey maps Downs at the center of ZIP 52162: silt loam, well drained, pH about 6.2 (slightly acidic).

Did spring come early in Postville, IA in 2026?

Spring leaf-out near 52162 came on Mar 30 in 2026, 14 days earlier than the 1991–2020 average (Apr 13), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Postville, IA?

Long-day onions: the longest day near 52162 is 15 h 23 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 52162 change?

Yes. The 2012 USDA map put 52162 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.