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

Planting zone for 50523 — Callender, IA

ZIP code 50523 (Callender, Webster County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is April 28 and the first fall frost October 8.

Where ZIP 50523 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 28
First frostOct 8
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 Callender, 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 Callender, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 28median — 50% chance of a later frost
Safe for tender plantsMay 9only 10% chance of frost after
First fall frostOctober 8median — 10% chance by Sep 24
Growing season162 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 17 and returns around October 19.

From the NOAA station Ft Dodge 5nnw, IA — 16 miles away, elevation 1,116 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 50523

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 17 – Mar 31
SpinachSow outdoors · Mar 17 – Apr 7
Broccoli, cabbageStart indoors · Feb 17 – Mar 3
Broccoli, cabbageTransplant · Apr 7 – Apr 21
Onion setsPlant outdoors · Mar 31 – Apr 14
PotatoesPlant outdoors · Apr 7 – Apr 21
LettuceSow outdoors · Mar 31 – Apr 14
Carrots, beetsSow outdoors · Apr 7 – Apr 21
TomatoesStart indoors · Mar 3 – Mar 17
TomatoesTransplant · May 5 – May 19
Peppers, eggplantStart indoors · Feb 17 – Mar 3
Peppers, eggplantTransplant · May 12 – May 26
BeansSow outdoors · May 5 – May 19
Sweet cornSow outdoors · May 5 – May 19
Cucumbers, squashSow outdoors · May 5 – May 19
Fall lettuce, spinachSow outdoors · Aug 13 – Aug 27
GarlicPlant cloves · Sep 24 – Oct 29
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 28) and first fall frost (Oct 8) 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 50523 came on Mar 25 — 15 days earlier than the 1991–2020 average (Apr 9).

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 Callender, IA.

Soil in Callender, IA

The soil mapped at the center of ZIP 50523 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 50523; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Callender, IA

Summer high83 °Faverage high, July
Winter low7 °Faverage low, January
Hot days11days a year at 90 °F or more
Freezing nights157nights a year at 32 °F or less
Growing degree days2,777base 50 °F — the season’s usable heat
Longest day15 h 17 mindaylight on June 21
Shortest day9 h 04 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation35 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 26 °F, low 7 °F 26°7° JanFebruary: average high 31 °F, low 12 °F 31°12° FebMarch: average high 44 °F, low 24 °F 44°24° MarApril: average high 59 °F, low 35 °F 59°35° AprMay: average high 70 °F, low 48 °F 70°48° MayJune: average high 80 °F, low 58 °F 80°58° JunJuly: average high 83 °F, low 62 °F 83°62° JulAugust: average high 80 °F, low 60 °F 80°60° AugSeptember: average high 74 °F, low 51 °F 74°51° SepOctober: average high 61 °F, low 38 °F 61°38° OctNovember: average high 45 °F, low 25 °F 45°25° NovDecember: average high 31 °F, low 14 °F 31°14° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 0.88 in precipitation 0.9 JanFebruary: 0.65 in precipitation 0.7 FebMarch: 1.92 in precipitation 1.9 MarApril: 3.72 in precipitation 3.7 AprMay: 5.04 in precipitation 5.0 MayJune: 5.33 in precipitation 5.3 JunJuly: 4.07 in precipitation 4.1 JulAugust: 4.89 in precipitation 4.9 AugSeptember: 3.01 in precipitation 3.0 SepOctober: 2.63 in precipitation 2.6 OctNovember: 1.59 in precipitation 1.6 NovDecember: 1.27 in precipitation 1.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Ft Dodge 5nnw, IA (16 mi away); precipitation: Fort Dodge 5.6 Wnw, IA (12 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

505665a
Moorland, IA · 5 mi
505435a
Gowrie, IA · 6 mi
505865a
Somers, IA · 7 mi
505695a
Otho, IA · 8 mi
505385a
Farnhamville, IA · 9 mi
505215a
Burnside, IA · 10 mi
505445a
Harcourt, IA · 10 mi
505015a
Fort Dodge, IA · 10 mi

Iowa planting zones →

Questions about 50523

What planting zone is ZIP code 50523?

ZIP code 50523 (Callender, 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 Callender, IA?

The median last spring frost (32 °F) near 50523 is April 28; after May 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Ft Dodge 5nnw station.

When is the first frost in Callender, IA?

The median first fall frost near 50523 is October 8, giving a median frost-free growing season of 162 days.

When should I plant tomatoes in 50523?

Start tomato seeds indoors around Mar 3 – Mar 17 and set transplants outside around May 5 – May 19, one to three weeks after the median last frost.

How much rain and snow does 50523 get?

About 35 inches of precipitation a year (NOAA 1991–2020 normals, Fort Dodge 5.6 Wnw station).

How hot do summers get in Callender, IA?

The average high peaks at 83 °F in July, with about 11 days a year at 90 °F or more.

What kind of soil does 50523 have?

The USDA soil survey maps Webster at the center of ZIP 50523: clay loam, poorly drained, pH about 6.5 (neutral).

Did spring come early in Callender, IA in 2026?

Spring leaf-out near 50523 came on Mar 25 in 2026, 15 days earlier than the 1991–2020 average (Apr 9), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Callender, IA?

Long-day onions: the longest day near 50523 is 15 h 17 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).