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

Planting zone for 50226 — Polk City, IA

ZIP code 50226 (Polk City, Polk County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is April 19 and the first fall frost October 18.

Where ZIP 50226 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.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostApr 19
First frostOct 18
2012 zone5a

Was 5a 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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Polk City, 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 Polk City, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 19median — 50% chance of a later frost
Safe for tender plantsMay 3only 10% chance of frost after
First fall frostOctober 18median — 10% chance by Oct 1
Growing season179 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 9 and returns around October 27.

From the NOAA station Des Moines Wsfo-Johnston, IA — 4 miles away, elevation 958 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 50226

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 8 – Mar 22
SpinachSow outdoors · Mar 8 – Mar 29
Broccoli, cabbageStart indoors · Feb 8 – Feb 22
Broccoli, cabbageTransplant · Mar 29 – Apr 12
Onion setsPlant outdoors · Mar 22 – Apr 5
PotatoesPlant outdoors · Mar 29 – Apr 12
LettuceSow outdoors · Mar 22 – Apr 5
Carrots, beetsSow outdoors · Mar 29 – Apr 12
TomatoesStart indoors · Feb 22 – Mar 8
TomatoesTransplant · Apr 26 – May 10
Peppers, eggplantStart indoors · Feb 8 – Feb 22
Peppers, eggplantTransplant · May 3 – May 17
BeansSow outdoors · Apr 26 – May 10
Sweet cornSow outdoors · Apr 26 – May 10
Cucumbers, squashSow outdoors · Apr 26 – May 10
Fall lettuce, spinachSow outdoors · Aug 23 – Sep 6
GarlicPlant cloves · Oct 4 – Nov 8
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 19) and first fall frost (Oct 18) 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 50226 came on Mar 23 — 13 days earlier than the 1991–2020 average (Apr 5).

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 5b in Iowa

473 plants native to the lower 48 states, recorded in Iowa, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. Each links to its USDA PLANTS profile.

Trees 49

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 191

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 136

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 Polk City, IA.

Soil in Polk City, IA

The soil mapped at the center of ZIP 50226 is Storden — loam, well drained.

TextureLoama good balance for most vegetables
pH7.7slightly alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupBwater soaks in moderately
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Storden loam, Bemis moraine, 10 to 16 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 50226; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Polk City, IA

Summer high85 °Faverage high, July
Winter low13 °Faverage low, January
Hot days18days a year at 90 °F or more
Freezing nights135nights a year at 32 °F or less
Growing degree days3,361base 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)
Precipitation36.2 inper year, rain and melted snow
Snowfall38 inper year; 55 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 30 °F, low 13 °F 30°13° JanFebruary: average high 35 °F, low 17 °F 35°17° FebMarch: average high 49 °F, low 29 °F 49°29° MarApril: average high 62 °F, low 40 °F 62°40° AprMay: average high 72 °F, low 52 °F 72°52° MayJune: average high 81 °F, low 62 °F 81°62° JunJuly: average high 85 °F, low 66 °F 85°66° JulAugust: average high 83 °F, low 64 °F 83°64° AugSeptember: average high 76 °F, low 55 °F 76°55° SepOctober: average high 63 °F, low 43 °F 63°43° OctNovember: average high 48 °F, low 30 °F 48°30° NovDecember: average high 35 °F, low 19 °F 35°19° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 1.01 in precipitation, 9.7 in snowfall 1.0❄10 JanFebruary: 1.25 in precipitation, 10.5 in snowfall 1.3❄11 FebMarch: 2.15 in precipitation, 5 in snowfall 2.1❄5 MarApril: 4.00 in precipitation, 1.6 in snowfall 4.0❄2 AprMay: 4.84 in precipitation, 0.2 in snowfall 4.8 MayJune: 5.35 in precipitation 5.3 JunJuly: 4.27 in precipitation 4.3 JulAugust: 3.97 in precipitation 4.0 AugSeptember: 3.40 in precipitation 3.4 SepOctober: 2.51 in precipitation, 0.5 in snowfall 2.5❄1 OctNovember: 1.95 in precipitation, 2.2 in snowfall 1.9❄2 NovDecember: 1.46 in precipitation, 8.3 in snowfall 1.5❄8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Des Moines Wsfo-Johnston, IA (4 mi away); precipitation: Des Moines Wsfo-Johnston, IA (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

502445b
Slater, IA · 5 mi
502435b
Sheldahl, IA · 5 mi
500075b
Alleman, IA · 5 mi
501095b
Granger, IA · 5 mi
500235b
Ankeny, IA · 6 mi
501315b
Johnston, IA · 7 mi
501245b
Huxley, IA · 8 mi
500215b
Ankeny, IA · 9 mi

Iowa planting zones →

Questions about 50226

What planting zone is ZIP code 50226?

ZIP code 50226 (Polk City, IA) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Polk City, IA?

The median last spring frost (32 °F) near 50226 is April 19; after May 3 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Des Moines Wsfo-Johnston station.

When is the first frost in Polk City, IA?

The median first fall frost near 50226 is October 18, giving a median frost-free growing season of 179 days.

When should I plant tomatoes in 50226?

Start tomato seeds indoors around Feb 22 – Mar 8 and set transplants outside around Apr 26 – May 10, one to three weeks after the median last frost.

How much rain and snow does 50226 get?

About 36.2 inches of precipitation a year and 38 inches of snowfall (NOAA 1991–2020 normals, Des Moines Wsfo-Johnston station).

How hot do summers get in Polk City, IA?

The average high peaks at 85 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 50226 have?

The USDA soil survey maps Storden at the center of ZIP 50226: loam, well drained, pH about 7.7 (slightly alkaline).

Did spring come early in Polk City, IA in 2026?

Spring leaf-out near 50226 came on Mar 23 in 2026, 13 days earlier than the 1991–2020 average (Apr 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Polk City, IA?

Long-day onions: the longest day near 50226 is 15 h 13 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 50226 change?

Yes. The 2012 USDA map put 50226 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.