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

Planting zone for 50599 — Woolstock, IA

ZIP code 50599 (Woolstock, Wright County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 3 and the first fall frost October 2.

Where ZIP 50599 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 3
First frostOct 2
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 Woolstock, 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 Woolstock, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 3median — 50% chance of a later frost
Safe for tender plantsMay 16only 10% chance of frost after
First fall frostOctober 2median — 10% chance by Sep 18
Growing season150 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 24 and returns around October 12.

From the NOAA station Webster City, IA — 7 miles away, elevation 1,073 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 50599

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 22 – Apr 5
SpinachSow outdoors · Mar 22 – Apr 12
Broccoli, cabbageStart indoors · Feb 22 – Mar 8
Broccoli, cabbageTransplant · Apr 12 – Apr 26
Onion setsPlant outdoors · Apr 5 – Apr 19
PotatoesPlant outdoors · Apr 12 – Apr 26
LettuceSow outdoors · Apr 5 – Apr 19
Carrots, beetsSow outdoors · Apr 12 – Apr 26
TomatoesStart indoors · Mar 8 – Mar 22
TomatoesTransplant · May 10 – May 24
Peppers, eggplantStart indoors · Feb 22 – Mar 8
Peppers, eggplantTransplant · May 17 – May 31
BeansSow outdoors · May 10 – May 24
Sweet cornSow outdoors · May 10 – May 24
Cucumbers, squashSow outdoors · May 10 – May 24
Fall lettuce, spinachSow outdoors · Aug 7 – Aug 21
GarlicPlant cloves · Sep 18 – Oct 23
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 3) and first fall frost (Oct 2) 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 50599 came on Mar 25 — 16 days earlier than the 1991–2020 average (Apr 10).

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 Woolstock, IA.

Soil in Woolstock, IA

The soil mapped at the center of ZIP 50599 is Harps — 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: Harps 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 50599; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Woolstock, IA

Summer high83 °Faverage high, July
Winter low7 °Faverage low, January
Hot days13days a year at 90 °F or more
Freezing nights160nights a year at 32 °F or less
Growing degree days2,678base 50 °F — the season’s usable heat
Longest day15 h 19 mindaylight on June 21
Shortest day9 h 03 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation37.2 inper year, rain and melted snow
Snowfall33 inper year; 68 days with snow on the ground

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 11 °F 31°11° FebMarch: average high 44 °F, low 23 °F 44°23° MarApril: average high 59 °F, low 34 °F 59°34° AprMay: average high 70 °F, low 47 °F 70°47° MayJune: average high 80 °F, low 57 °F 80°57° JunJuly: average high 83 °F, low 61 °F 83°61° JulAugust: average high 81 °F, low 58 °F 81°58° AugSeptember: average high 75 °F, low 49 °F 75°49° SepOctober: average high 62 °F, low 37 °F 62°37° OctNovember: average high 45 °F, low 24 °F 45°24° NovDecember: average high 32 °F, low 13 °F 32°13° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 0.87 in precipitation, 7.9 in snowfall 0.9❄8 JanFebruary: 1.34 in precipitation, 9.8 in snowfall 1.3❄10 FebMarch: 2.05 in precipitation, 4.4 in snowfall 2.0❄4 MarApril: 3.72 in precipitation, 1 in snowfall 3.7❄1 AprMay: 5.27 in precipitation, 0.2 in snowfall 5.3 MayJune: 5.76 in precipitation 5.8 JunJuly: 4.41 in precipitation 4.4 JulAugust: 4.75 in precipitation 4.8 AugSeptember: 3.36 in precipitation 3.4 SepOctober: 2.65 in precipitation, 0.1 in snowfall 2.6 OctNovember: 1.70 in precipitation, 1.4 in snowfall 1.7❄1 NovDecember: 1.36 in precipitation, 8.1 in snowfall 1.4❄8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Webster City, IA (7 mi away); precipitation: Webster City, IA (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

505335a
Eagle Grove, IA · 7 mi
505955a
Webster City, IA · 8 mi
500345a
Blairsburg, IA · 9 mi
505945a
Vincent, IA · 11 mi
501015a
Galt, IA · 11 mi
505265a
Clarion, IA · 12 mi
505255a
Clarion, IA · 12 mi
505325a
Duncombe, IA · 12 mi

Iowa planting zones →

Questions about 50599

What planting zone is ZIP code 50599?

ZIP code 50599 (Woolstock, 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 Woolstock, IA?

The median last spring frost (32 °F) near 50599 is May 3; after May 16 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Webster City station.

When is the first frost in Woolstock, IA?

The median first fall frost near 50599 is October 2, giving a median frost-free growing season of 150 days.

When should I plant tomatoes in 50599?

Start tomato seeds indoors around Mar 8 – Mar 22 and set transplants outside around May 10 – May 24, one to three weeks after the median last frost.

How much rain and snow does 50599 get?

About 37.2 inches of precipitation a year and 33 inches of snowfall (NOAA 1991–2020 normals, Webster City station).

How hot do summers get in Woolstock, IA?

The average high peaks at 83 °F in July, with about 13 days a year at 90 °F or more.

What kind of soil does 50599 have?

The USDA soil survey maps Harps at the center of ZIP 50599: clay loam, poorly drained, pH about 7.5 (slightly alkaline).

Did spring come early in Woolstock, IA in 2026?

Spring leaf-out near 50599 came on Mar 25 in 2026, 16 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Woolstock, IA?

Long-day onions: the longest day near 50599 is 15 h 19 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).