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

Planting zone for 51009 — Calumet, IA

ZIP code 51009 (Calumet, O'Brien County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is April 29 and the first fall frost October 10.

Where ZIP 51009 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 29
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 Calumet, 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 Calumet, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 29median — 50% chance of a later frost
Safe for tender plantsMay 11only 10% chance of frost after
First fall frostOctober 10median — 10% chance by Sep 26
Growing season163 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 18 and returns around October 21.

From the NOAA station Primghar, IA — 11 miles away, elevation 1,519 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 51009

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 18 – Apr 1
SpinachSow outdoors · Mar 18 – Apr 8
Broccoli, cabbageStart indoors · Feb 18 – Mar 4
Broccoli, cabbageTransplant · Apr 8 – Apr 22
Onion setsPlant outdoors · Apr 1 – Apr 15
PotatoesPlant outdoors · Apr 8 – Apr 22
LettuceSow outdoors · Apr 1 – Apr 15
Carrots, beetsSow outdoors · Apr 8 – Apr 22
TomatoesStart indoors · Mar 4 – Mar 18
TomatoesTransplant · May 6 – May 20
Peppers, eggplantStart indoors · Feb 18 – Mar 4
Peppers, eggplantTransplant · May 13 – May 27
BeansSow outdoors · May 6 – May 20
Sweet cornSow outdoors · May 6 – May 20
Cucumbers, squashSow outdoors · May 6 – May 20
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 29) 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 51009 came on Mar 25 — 17 days earlier than the 1991–2020 average (Apr 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).

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 Calumet, IA.

Soil in Calumet, IA

The soil mapped at the center of ZIP 51009 is Primghar — silty clay loam, somewhat poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up
pH6.5neutral; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter6.2%high
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classprime farmlandUSDA classification

Map unit: Primghar silty 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 51009; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Calumet, IA

Summer high85 °Faverage high, July
Winter low9 °Faverage low, January
Hot days13days a year at 90 °F or more
Freezing nights153nights a year at 32 °F or less
Growing degree days3,146base 50 °F — the season’s usable heat
Longest day15 h 21 mindaylight on June 21
Shortest day9 h 00 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation31.4 inper year, rain and melted snow
Snowfall35 inper year

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 27 °F, low 9 °F 27°9° JanFebruary: average high 32 °F, low 14 °F 32°14° FebMarch: average high 46 °F, low 26 °F 46°26° MarApril: average high 61 °F, low 37 °F 61°37° AprMay: average high 72 °F, low 49 °F 72°49° MayJune: average high 82 °F, low 60 °F 82°60° JunJuly: average high 85 °F, low 64 °F 85°64° JulAugust: average high 82 °F, low 62 °F 82°62° AugSeptember: average high 76 °F, low 53 °F 76°53° SepOctober: average high 62 °F, low 40 °F 62°40° OctNovember: average high 45 °F, low 27 °F 45°27° NovDecember: average high 31 °F, low 15 °F 31°15° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 0.82 in precipitation, 8.4 in snowfall 0.8❄8 JanFebruary: 0.89 in precipitation, 6.7 in snowfall 0.9❄7 FebMarch: 1.70 in precipitation, 6.2 in snowfall 1.7❄6 MarApril: 3.30 in precipitation, 2.4 in snowfall 3.3❄2 AprMay: 4.11 in precipitation 4.1 MayJune: 4.98 in precipitation 5.0 JunJuly: 3.88 in precipitation 3.9 JulAugust: 3.58 in precipitation 3.6 AugSeptember: 3.30 in precipitation 3.3 SepOctober: 2.28 in precipitation, 0.4 in snowfall 2.3 OctNovember: 1.49 in precipitation, 2.5 in snowfall 1.5❄3 NovDecember: 1.02 in precipitation, 8.2 in snowfall 1.0❄8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Primghar, IA (11 mi away); precipitation: Primghar, IA (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

510295a
Larrabee, IA · 4 mi
510585a
Sutherland, IA · 5 mi
510465a
Paullina, IA · 7 mi
510475a
Peterson, IA · 9 mi
510375a
Meriden, IA · 9 mi
512455a
Primghar, IA · 10 mi
510145a
Cleghorn, IA · 13 mi
510125a
Cherokee, IA · 14 mi

Iowa planting zones →

Questions about 51009

What planting zone is ZIP code 51009?

ZIP code 51009 (Calumet, 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 Calumet, IA?

The median last spring frost (32 °F) near 51009 is April 29; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Primghar station.

When is the first frost in Calumet, IA?

The median first fall frost near 51009 is October 10, giving a median frost-free growing season of 163 days.

When should I plant tomatoes in 51009?

Start tomato seeds indoors around Mar 4 – Mar 18 and set transplants outside around May 6 – May 20, one to three weeks after the median last frost.

How much rain and snow does 51009 get?

About 31.4 inches of precipitation a year and 35 inches of snowfall (NOAA 1991–2020 normals, Primghar station).

How hot do summers get in Calumet, IA?

The average high peaks at 85 °F in July, with about 13 days a year at 90 °F or more.

What kind of soil does 51009 have?

The USDA soil survey maps Primghar at the center of ZIP 51009: silty clay loam, somewhat poorly drained, pH about 6.5 (neutral).

Did spring come early in Calumet, IA in 2026?

Spring leaf-out near 51009 came on Mar 25 in 2026, 17 days earlier than the 1991–2020 average (Apr 11), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Calumet, IA?

Long-day onions: the longest day near 51009 is 15 h 21 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).