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

Planting zone for 51355 — Okoboji, IA

ZIP code 51355 (Okoboji, Dickinson 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 6.

Where ZIP 51355 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 6

2012 zone5a

Same zone as on the 2012 map. 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 Okoboji, 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 Okoboji, 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 6median — 10% chance by Sep 24

Growing season158 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 21 and returns around October 17.

From the NOAA station Milford 4 Nw, IA — 2 miles away, elevation 1,401 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 51355

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 11 – Aug 25

GarlicPlant cloves · Sep 22 – Oct 27

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 1) and first fall frost (Oct 6) 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 51355 came on Mar 25 — 21 days earlier than the 1991–2020 average (Apr 15).

average
Apr 152026
Mar 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 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 Okoboji, IA.

Soil in Okoboji, IA

The soil mapped at the center of ZIP 51355 is Webster — clay loam, poorly drained.

TextureClay loamholds water and nutrients; slow to drain and warm up

pH6.5neutral; most vegetables like 6.0–7.0

DrainagePoorly drainedconsider raised beds

Organic matter7%high

Hydrologic groupC/Dslow when drained; wet otherwise

Farmland classPrime farmland if drainedUSDA classification

Map unit: Webster clay loam, 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 51355; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Okoboji, IA

Summer high83 °Faverage high, July

Winter low8 °Faverage low, January

Hot days10days a year at 90 °F or more

Freezing nights159nights a year at 32 °F or less

Growing degree days2,777base 50 °F — the season’s usable heat

Longest day15 h 25 mindaylight on June 21

Shortest day8 h 57 mindaylight on December 21

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

Precipitation29.5 inper year, rain and melted snow

Snowfall38 inper year; 81 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: Milford 4 Nw, IA (2 mi away); precipitation: Milford 4 Nw, IA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

513315a

Arnolds Park, IA · 2 mi

513605a

Spirit Lake, IA · 4 mi

Iowa planting zones →

Questions about 51355

What planting zone is ZIP code 51355?

ZIP code 51355 (Okoboji, 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 Okoboji, IA?

The median last spring frost (32 °F) near 51355 is May 1; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Milford 4 Nw station.

When is the first frost in Okoboji, IA?

The median first fall frost near 51355 is October 6, giving a median frost-free growing season of 158 days.

When should I plant tomatoes in 51355?

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 51355 get?

About 29.5 inches of precipitation a year and 38 inches of snowfall (NOAA 1991–2020 normals, Milford 4 Nw station).

How hot do summers get in Okoboji, IA?

The average high peaks at 83 °F in July, with about 10 days a year at 90 °F or more.

What kind of soil does 51355 have?

The USDA soil survey maps Webster at the center of ZIP 51355: clay loam, poorly drained, pH about 6.5 (neutral).

Did spring come early in Okoboji, IA in 2026?

Spring leaf-out near 51355 came on Mar 25 in 2026, 21 days earlier than the 1991–2020 average (Apr 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Okoboji, IA?

Long-day onions: the longest day near 51355 is 15 h 25 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).