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

Planting zone for 51545 — Little Sioux, IA

ZIP code 51545 (Little Sioux, Harrison 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 51545 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 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 Little Sioux, 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 Little Sioux, 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 12only 10% chance of frost after
First fall frostOctober 3median — 10% chance by Sep 20
Growing season155 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 14.

From the NOAA station Little Sioux 2 Nw, IA — 2 miles away, elevation 1,024 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 51545

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 51545 came on Mar 19 — 16 days earlier than the 1991–2020 average (Apr 4).

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.

Trees 46

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Farborvitae50 ft · blooms mid spring · medium shade tolerance · to −33 °Fbalsam fir60 ft · blooms mid summer · low shade tolerance · to −43 °F

Shrubs 77

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °FAllegheny serviceberry35 ft · blooms early spring · low shade tolerance · to −38 °Falternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican hornbeam30 ft · blooms mid spring · low shade tolerance · to −34 °F

Wildflowers & perennials 185

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °F

Grasses 133

arctic brome3 ft · blooms early summer · low shade tolerance · to −33 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBebb's sedge3 ft · blooms late spring · low shade tolerance · to −38 °FBicknell's sedge3 ft · blooms late spring · low shade tolerance · to −38 °Fbig bluestem6 ft · blooms summer · high shade tolerance · to −46 °Fblue grama1 ft · blooms early summer · high shade tolerance · to −43 °F

Vines 7

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fsummer grape30 ft · blooms late spring · low shade tolerance · to −23 °Ftrumpet honeysuckle16 ft · blooms late summer · low shade tolerance · to −33 °F

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 Little Sioux, IA.

Soil in Little Sioux, IA

The soil mapped at the center of ZIP 51545 is Albaton — silty clay, poorly drained.

TextureSilty clayholds water and nutrients; slow to drain and warm up
pH7.2neutral; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter2.5%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Albaton silty clay, 0 to 2 percent slopes, occasionally flooded.

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 51545; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Little Sioux, IA

Summer high86 °Faverage high, July
Winter low9 °Faverage low, January
Hot days26days a year at 90 °F or more
Freezing nights165nights a year at 32 °F or less
Growing degree days3,075base 50 °F — the season’s usable heat
Longest day15 h 13 mindaylight on June 21
Shortest day9 h 08 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation39.8 inper year, rain and melted snow
Snowfall46 inper year; 61 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 29 °F, low 9 °F 29°9° JanFebruary: average high 34 °F, low 13 °F 34°13° FebMarch: average high 48 °F, low 24 °F 48°24° MarApril: average high 62 °F, low 35 °F 62°35° AprMay: average high 73 °F, low 48 °F 73°48° MayJune: average high 83 °F, low 59 °F 83°59° JunJuly: average high 86 °F, low 62 °F 86°62° JulAugust: average high 83 °F, low 60 °F 83°60° AugSeptember: average high 77 °F, low 50 °F 77°50° SepOctober: average high 64 °F, low 37 °F 64°37° OctNovember: average high 48 °F, low 24 °F 48°24° NovDecember: average high 34 °F, low 14 °F 34°14° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 0.92 in precipitation, 10 in snowfall 0.9❄10 JanFebruary: 1.30 in precipitation, 13.4 in snowfall 1.3❄13 FebMarch: 2.28 in precipitation, 6.9 in snowfall 2.3❄7 MarApril: 3.87 in precipitation, 1.9 in snowfall 3.9❄2 AprMay: 5.06 in precipitation, 0.3 in snowfall 5.1 MayJune: 5.72 in precipitation 5.7 JunJuly: 4.85 in precipitation 4.8 JulAugust: 4.54 in precipitation 4.5 AugSeptember: 5.05 in precipitation 5.0 SepOctober: 2.93 in precipitation, 1 in snowfall 2.9❄1 OctNovember: 1.74 in precipitation, 2.3 in snowfall 1.7❄2 NovDecember: 1.50 in precipitation, 9.8 in snowfall 1.5❄10 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Little Sioux 2 Nw, IA (2 mi away); precipitation: Little Sioux 2 Nw, IA (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

515235a
Blencoe, IA · 5 mi
515645b
Pisgah, IA · 6 mi
515575b
Mondamin, IA · 8 mi
515585b
Moorhead, IA · 8 mi
680615b
Tekamah, NE · 11 mi
510405a
Onawa, IA · 13 mi
515505b
Magnolia, IA · 13 mi
515725b
Soldier, IA · 14 mi

Iowa planting zones →

Questions about 51545

What planting zone is ZIP code 51545?

ZIP code 51545 (Little Sioux, 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 Little Sioux, IA?

The median last spring frost (32 °F) near 51545 is May 1; after May 12 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Little Sioux 2 Nw station.

When is the first frost in Little Sioux, IA?

The median first fall frost near 51545 is October 3, giving a median frost-free growing season of 155 days.

When should I plant tomatoes in 51545?

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 51545 get?

About 39.8 inches of precipitation a year and 46 inches of snowfall (NOAA 1991–2020 normals, Little Sioux 2 Nw station).

How hot do summers get in Little Sioux, IA?

The average high peaks at 86 °F in July, with about 26 days a year at 90 °F or more.

What kind of soil does 51545 have?

The USDA soil survey maps Albaton at the center of ZIP 51545: silty clay, poorly drained, pH about 7.2 (neutral).

Did spring come early in Little Sioux, IA in 2026?

Spring leaf-out near 51545 came on Mar 19 in 2026, 16 days earlier than the 1991–2020 average (Apr 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Little Sioux, IA?

Long-day onions: the longest day near 51545 is 15 h 13 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).