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

Planting zone for 51534 — Glenwood, IA

ZIP code 51534 (Glenwood, Mills County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 23 and the first fall frost October 11.

Where ZIP 51534 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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostApr 23
First frostOct 11
2012 zone5a

Was 5a on the 2012 map — a full zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Glenwood, 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 Glenwood, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 23median — 50% chance of a later frost
Safe for tender plantsMay 6only 10% chance of frost after
First fall frostOctober 11median — 10% chance by Sep 27
Growing season170 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 12 and returns around October 21.

From the NOAA station Glenwood 3sw, IA — 4 miles away, elevation 981 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 51534

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 12 – Mar 26
SpinachSow outdoors · Mar 12 – Apr 2
Broccoli, cabbageStart indoors · Feb 12 – Feb 26
Broccoli, cabbageTransplant · Apr 2 – Apr 16
Onion setsPlant outdoors · Mar 26 – Apr 9
PotatoesPlant outdoors · Apr 2 – Apr 16
LettuceSow outdoors · Mar 26 – Apr 9
Carrots, beetsSow outdoors · Apr 2 – Apr 16
TomatoesStart indoors · Feb 26 – Mar 12
TomatoesTransplant · Apr 30 – May 14
Peppers, eggplantStart indoors · Feb 12 – Feb 26
Peppers, eggplantTransplant · May 7 – May 21
BeansSow outdoors · Apr 30 – May 14
Sweet cornSow outdoors · Apr 30 – May 14
Cucumbers, squashSow outdoors · Apr 30 – May 14
Fall lettuce, spinachSow outdoors · Aug 16 – Aug 30
GarlicPlant cloves · Sep 27 – Nov 1
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 23) and first fall frost (Oct 11) 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 51534 came on Mar 11 — 18 days earlier than the 1991–2020 average (Mar 29).

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 6a in Iowa

482 plants native to the lower 48 states, recorded in Iowa, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. 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 79

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 195

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 137

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 8

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 creeper2 ft · blooms summer · high shade tolerance · to −13 °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 Glenwood, IA.

Soil in Glenwood, IA

The soil mapped at the center of ZIP 51534 is Monona — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH6.1slightly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Monona silt loam, 9 to 14 percent slopes, severely 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 51534; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Glenwood, IA

Summer high87 °Faverage high, July
Winter low12 °Faverage low, January
Hot days34days a year at 90 °F or more
Freezing nights146nights a year at 32 °F or less
Growing degree days3,476base 50 °F — the season’s usable heat
Longest day15 h 08 mindaylight on June 21
Shortest day9 h 13 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation34.8 inper year, rain and melted snow
Snowfall24 inper year; 37 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 33 °F, low 12 °F 33°12° JanFebruary: average high 38 °F, low 16 °F 38°16° FebMarch: average high 52 °F, low 28 °F 52°28° MarApril: average high 64 °F, low 38 °F 64°38° AprMay: average high 74 °F, low 50 °F 74°50° MayJune: average high 83 °F, low 61 °F 83°61° JunJuly: average high 87 °F, low 65 °F 87°65° JulAugust: average high 85 °F, low 62 °F 85°62° AugSeptember: average high 79 °F, low 53 °F 79°53° SepOctober: average high 67 °F, low 40 °F 67°40° OctNovember: average high 51 °F, low 28 °F 51°28° NovDecember: average high 38 °F, low 18 °F 38°18° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 0.66 in precipitation, 8.2 in snowfall 0.7❄8 JanFebruary: 1.03 in precipitation, 7 in snowfall 1.0❄7 FebMarch: 2.03 in precipitation, 3.4 in snowfall 2.0❄3 MarApril: 3.73 in precipitation, 0.4 in snowfall 3.7 AprMay: 5.19 in precipitation 5.2 MayJune: 5.96 in precipitation 6.0 JunJuly: 4.31 in precipitation 4.3 JulAugust: 3.81 in precipitation 3.8 AugSeptember: 3.32 in precipitation 3.3 SepOctober: 2.30 in precipitation 2.3 OctNovember: 1.30 in precipitation, 1.3 in snowfall 1.3❄1 NovDecember: 1.16 in precipitation, 3.4 in snowfall 1.2❄3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Glenwood 3sw, IA (4 mi away); precipitation: Glenwood 3sw, IA (4 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.

515615b
Pacific Junction, IA · 5 mi
515545b
Mineola, IA · 7 mi
515515b
Malvern, IA · 8 mi
515716a
Silver City, IA · 9 mi
681135b
Offutt Afb, NE · 11 mi
516536a
Tabor, IA · 11 mi
680055b
Bellevue, NE · 11 mi
515405b
Hastings, IA · 12 mi

Iowa planting zones →

Questions about 51534

What planting zone is ZIP code 51534?

ZIP code 51534 (Glenwood, IA) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Glenwood, IA?

The median last spring frost (32 °F) near 51534 is April 23; after May 6 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Glenwood 3sw station.

When is the first frost in Glenwood, IA?

The median first fall frost near 51534 is October 11, giving a median frost-free growing season of 170 days.

When should I plant tomatoes in 51534?

Start tomato seeds indoors around Feb 26 – Mar 12 and set transplants outside around Apr 30 – May 14, one to three weeks after the median last frost.

How much rain and snow does 51534 get?

About 34.8 inches of precipitation a year and 24 inches of snowfall (NOAA 1991–2020 normals, Glenwood 3sw station).

How hot do summers get in Glenwood, IA?

The average high peaks at 87 °F in July, with about 34 days a year at 90 °F or more.

What kind of soil does 51534 have?

The USDA soil survey maps Monona at the center of ZIP 51534: silt loam, well drained, pH about 6.1 (slightly acidic).

Did spring come early in Glenwood, IA in 2026?

Spring leaf-out near 51534 came on Mar 11 in 2026, 18 days earlier than the 1991–2020 average (Mar 29), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Glenwood, IA?

Long-day onions: the longest day near 51534 is 15 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 51534 change?

Yes. The 2012 USDA map put 51534 in zone 5a; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.