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

Planting zone for 51459 — Ralston, IA

ZIP code 51459 (Ralston, Carroll County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is April 27 and the first fall frost October 10.

Where ZIP 51459 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 frostApr 27

First frostOct 10

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 Ralston, 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 Ralston, IA

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 27median — 50% chance of a later frost

Safe for tender plantsMay 8only 10% chance of frost after

First fall frostOctober 10median — 10% chance by Sep 25

Growing season166 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 16 and returns around October 21.

From the NOAA station Carroll, IA — 11 miles away, elevation 1,240 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 51459

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 16 – Mar 30

SpinachSow outdoors · Mar 16 – Apr 6

Broccoli, cabbageStart indoors · Feb 16 – Mar 2

Broccoli, cabbageTransplant · Apr 6 – Apr 20

Onion setsPlant outdoors · Mar 30 – Apr 13

PotatoesPlant outdoors · Apr 6 – Apr 20

LettuceSow outdoors · Mar 30 – Apr 13

Carrots, beetsSow outdoors · Apr 6 – Apr 20

TomatoesStart indoors · Mar 2 – Mar 16

TomatoesTransplant · May 4 – May 18

Peppers, eggplantStart indoors · Feb 16 – Mar 2

Peppers, eggplantTransplant · May 11 – May 25

BeansSow outdoors · May 4 – May 18

Sweet cornSow outdoors · May 4 – May 18

Cucumbers, squashSow outdoors · May 4 – May 18

Fall lettuce, spinachSow outdoors · Aug 15 – Aug 29

GarlicPlant cloves · Sep 26 – Oct 31

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 27) and first fall frost (Oct 10) 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 51459 came on Mar 24 — 14 days earlier than the 1991–2020 average (Apr 7).

average
Apr 72026
Mar 24

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 Ralston, IA

The soil mapped at the center of ZIP 51459 is Canisteo — clay loam, poorly drained.

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

pH7.5slightly alkaline; 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: Canisteo clay loam, Bemis moraine, 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 51459; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ralston, IA

Summer high84 °Faverage high, July

Winter low10 °Faverage low, January

Hot days18days a year at 90 °F or more

Freezing nights153nights a year at 32 °F or less

Growing degree days3,081base 50 °F — the season’s usable heat

Longest day15 h 15 mindaylight on June 21

Shortest day9 h 06 mindaylight on December 21

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

Precipitation33.7 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: Carroll, IA (11 mi away); precipitation: Carroll, IA (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

Lidderdale, IA · 9 mi

514515a

Lanesboro, IA · 10 mi

Coon Rapids, IA · 13 mi

Iowa planting zones →

Questions about 51459

What planting zone is ZIP code 51459?

ZIP code 51459 (Ralston, 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 Ralston, IA?

The median last spring frost (32 °F) near 51459 is April 27; after May 8 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Carroll station.

When is the first frost in Ralston, IA?

The median first fall frost near 51459 is October 10, giving a median frost-free growing season of 166 days.

When should I plant tomatoes in 51459?

Start tomato seeds indoors around Mar 2 – Mar 16 and set transplants outside around May 4 – May 18, one to three weeks after the median last frost.

How much rain and snow does 51459 get?

About 33.7 inches of precipitation a year (NOAA 1991–2020 normals, Carroll station).

How hot do summers get in Ralston, IA?

The average high peaks at 84 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 51459 have?

The USDA soil survey maps Canisteo at the center of ZIP 51459: clay loam, poorly drained, pH about 7.5 (slightly alkaline).

Did spring come early in Ralston, IA in 2026?

Spring leaf-out near 51459 came on Mar 24 in 2026, 14 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ralston, IA?

Long-day onions: the longest day near 51459 is 15 h 15 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).