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

Planting zone for 50514 — Armstrong, IA

ZIP code 50514 (Armstrong, Emmet County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 4 and the first fall frost October 1.

Where ZIP 50514 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 4
First frostOct 1
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 Armstrong, 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 Armstrong, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 4median — 50% chance of a later frost
Safe for tender plantsMay 14only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 18
Growing season150 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 25 and returns around October 10.

From the NOAA station Swea City 5n, IA — 9 miles away, elevation 1,181 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 50514

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 23 – Apr 6
SpinachSow outdoors · Mar 23 – Apr 13
Broccoli, cabbageStart indoors · Feb 23 – Mar 9
Broccoli, cabbageTransplant · Apr 13 – Apr 27
Onion setsPlant outdoors · Apr 6 – Apr 20
PotatoesPlant outdoors · Apr 13 – Apr 27
LettuceSow outdoors · Apr 6 – Apr 20
Carrots, beetsSow outdoors · Apr 13 – Apr 27
TomatoesStart indoors · Mar 9 – Mar 23
TomatoesTransplant · May 11 – May 25
Peppers, eggplantStart indoors · Feb 23 – Mar 9
Peppers, eggplantTransplant · May 18 – Jun 1
BeansSow outdoors · May 11 – May 25
Sweet cornSow outdoors · May 11 – May 25
Cucumbers, squashSow outdoors · May 11 – May 25
Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20
GarlicPlant cloves · Sep 17 – Oct 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 4) and first fall frost (Oct 1) 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 50514 came on Mar 28 — 17 days earlier than the 1991–2020 average (Apr 14).

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 Armstrong, IA.

Soil in Armstrong, IA

The soil mapped at the center of ZIP 50514 is Canisteo — 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: Canisteo 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 50514; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Armstrong, IA

Summer high81 °Faverage high, July
Winter low5 °Faverage low, January
Hot days11days a year at 90 °F or more
Freezing nights163nights a year at 32 °F or less
Growing degree days2,421base 50 °F — the season’s usable heat
Longest day15 h 25 mindaylight on June 21
Shortest day8 h 57 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation32.9 inper year, rain and melted snow
Snowfall40 inper year; 82 days with snow on the ground

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 22 °F, low 5 °F 22°5° JanFebruary: average high 27 °F, low 8 °F 27°8° FebMarch: average high 40 °F, low 21 °F 40°21° MarApril: average high 55 °F, low 33 °F 55°33° AprMay: average high 68 °F, low 46 °F 68°46° MayJune: average high 78 °F, low 57 °F 78°57° JunJuly: average high 81 °F, low 60 °F 81°60° JulAugust: average high 78 °F, low 58 °F 78°58° AugSeptember: average high 73 °F, low 48 °F 73°48° SepOctober: average high 59 °F, low 35 °F 59°35° OctNovember: average high 42 °F, low 22 °F 42°22° NovDecember: average high 28 °F, low 11 °F 28°11° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″January: 0.87 in precipitation, 10.9 in snowfall 0.9❄11 JanFebruary: 0.93 in precipitation, 8.5 in snowfall 0.9❄9 FebMarch: 1.76 in precipitation, 4.6 in snowfall 1.8❄5 MarApril: 3.43 in precipitation, 3.6 in snowfall 3.4❄4 AprMay: 4.60 in precipitation 4.6 MayJune: 4.65 in precipitation 4.7 JunJuly: 4.16 in precipitation 4.2 JulAugust: 4.11 in precipitation 4.1 AugSeptember: 3.21 in precipitation 3.2 SepOctober: 2.52 in precipitation, 0.7 in snowfall 2.5❄1 OctNovember: 1.46 in precipitation, 3.1 in snowfall 1.5❄3 NovDecember: 1.17 in precipitation, 8.3 in snowfall 1.2❄8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Swea City 5n, IA (9 mi away); precipitation: Swea City 5n, IA (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

505315a
Dolliver, IA · 7 mi
505785a
Ringsted, IA · 8 mi
505905a
Swea City, IA · 8 mi
561215a
Ceylon, MN · 10 mi
505395a
Fenton, IA · 13 mi
505565a
Ledyard, IA · 14 mi
505175a
Bancroft, IA · 14 mi
560315a
Fairmont, MN · 15 mi

Iowa planting zones →

Questions about 50514

What planting zone is ZIP code 50514?

ZIP code 50514 (Armstrong, 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 Armstrong, IA?

The median last spring frost (32 °F) near 50514 is May 4; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Swea City 5n station.

When is the first frost in Armstrong, IA?

The median first fall frost near 50514 is October 1, giving a median frost-free growing season of 150 days.

When should I plant tomatoes in 50514?

Start tomato seeds indoors around Mar 9 – Mar 23 and set transplants outside around May 11 – May 25, one to three weeks after the median last frost.

How much rain and snow does 50514 get?

About 32.9 inches of precipitation a year and 40 inches of snowfall (NOAA 1991–2020 normals, Swea City 5n station).

How hot do summers get in Armstrong, IA?

The average high peaks at 81 °F in July, with about 11 days a year at 90 °F or more.

What kind of soil does 50514 have?

The USDA soil survey maps Canisteo at the center of ZIP 50514: clay loam, poorly drained, pH about 7.5 (slightly alkaline).

Did spring come early in Armstrong, IA in 2026?

Spring leaf-out near 50514 came on Mar 28 in 2026, 17 days earlier than the 1991–2020 average (Apr 14), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Armstrong, IA?

Long-day onions: the longest day near 50514 is 15 h 25 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).