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

Planting zone for 52573 — Mount Sterling, IA

ZIP code 52573 (Mount Sterling, Van Buren County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 26 and the first fall frost October 13.

Where ZIP 52573 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 26
First frostOct 13
2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mount Sterling, 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 Mount Sterling, IA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 26median — 50% chance of a later frost
Safe for tender plantsMay 11only 10% chance of frost after
First fall frostOctober 13median — 10% chance by Sep 28
Growing season169 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 14 and returns around October 23.

From the NOAA station Keosauqua, IA — 7 miles away, elevation 630 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 52573

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 15 – Mar 29
SpinachSow outdoors · Mar 15 – Apr 5
Broccoli, cabbageStart indoors · Feb 15 – Mar 1
Broccoli, cabbageTransplant · Apr 5 – Apr 19
Onion setsPlant outdoors · Mar 29 – Apr 12
PotatoesPlant outdoors · Apr 5 – Apr 19
LettuceSow outdoors · Mar 29 – Apr 12
Carrots, beetsSow outdoors · Apr 5 – Apr 19
TomatoesStart indoors · Mar 1 – Mar 15
TomatoesTransplant · May 3 – May 17
Peppers, eggplantStart indoors · Feb 15 – Mar 1
Peppers, eggplantTransplant · May 10 – May 24
BeansSow outdoors · May 3 – May 17
Sweet cornSow outdoors · May 3 – May 17
Cucumbers, squashSow outdoors · May 3 – May 17
Fall lettuce, spinachSow outdoors · Aug 18 – Sep 1
GarlicPlant cloves · Sep 29 – Nov 3
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 26) and first fall frost (Oct 13) 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 52573 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).

Soil in Mount Sterling, IA

The soil mapped at the center of ZIP 52573 is Rinda — silty clay loam, poorly drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up
pH6.2slightly acidic; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter2.5%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Rinda silty clay loam, 5 to 9 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 52573; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Sterling, IA

Summer high86 °Faverage high, July
Winter low14 °Faverage low, January
Hot days32days a year at 90 °F or more
Freezing nights128nights a year at 32 °F or less
Growing degree days3,356base 50 °F — the season’s usable heat
Longest day15 h 05 mindaylight on June 21
Shortest day9 h 16 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation39.7 inper year, rain and melted snow
Snowfall23 inper year

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 32 °F, low 14 °F 32°14° JanFebruary: average high 37 °F, low 17 °F 37°17° FebMarch: average high 50 °F, low 29 °F 50°29° MarApril: average high 63 °F, low 39 °F 63°39° AprMay: average high 73 °F, low 51 °F 73°51° MayJune: average high 82 °F, low 60 °F 82°60° JunJuly: average high 86 °F, low 65 °F 86°65° JulAugust: average high 85 °F, low 62 °F 85°62° AugSeptember: average high 78 °F, low 53 °F 78°53° SepOctober: average high 65 °F, low 42 °F 65°42° OctNovember: average high 49 °F, low 29 °F 49°29° NovDecember: average high 37 °F, low 20 °F 37°20° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 1.50 in precipitation, 7.3 in snowfall 1.5❄7 JanFebruary: 2.11 in precipitation, 5.3 in snowfall 2.1❄5 FebMarch: 2.45 in precipitation, 2.7 in snowfall 2.5❄3 MarApril: 3.64 in precipitation, 0.9 in snowfall 3.6❄1 AprMay: 5.67 in precipitation 5.7 MayJune: 5.29 in precipitation 5.3 JunJuly: 4.48 in precipitation 4.5 JulAugust: 3.60 in precipitation 3.6 AugSeptember: 3.69 in precipitation 3.7 SepOctober: 2.97 in precipitation, 0.2 in snowfall 3.0 OctNovember: 2.35 in precipitation, 1.1 in snowfall 2.4❄1 NovDecember: 1.96 in precipitation, 5.5 in snowfall 2.0❄6 Dec

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

Nearby ZIP codes

2 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

525426a
Cantril, IA · 7 mi
525655b
Keosauqua, IA · 8 mi
526206a
Bonaparte, IA · 9 mi
634326a
Arbela, MO · 10 mi
634536a
Luray, MO · 10 mi
526266a
Farmington, IA · 11 mi
525705b
Milton, IA · 12 mi
634656a
Revere, MO · 15 mi

Iowa planting zones →

Questions about 52573

What planting zone is ZIP code 52573?

ZIP code 52573 (Mount Sterling, 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 Mount Sterling, IA?

The median last spring frost (32 °F) near 52573 is April 26; after May 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Keosauqua station.

When is the first frost in Mount Sterling, IA?

The median first fall frost near 52573 is October 13, giving a median frost-free growing season of 169 days.

When should I plant tomatoes in 52573?

Start tomato seeds indoors around Mar 1 – Mar 15 and set transplants outside around May 3 – May 17, one to three weeks after the median last frost.

How much rain and snow does 52573 get?

About 39.7 inches of precipitation a year and 23 inches of snowfall (NOAA 1991–2020 normals, Keosauqua station).

How hot do summers get in Mount Sterling, IA?

The average high peaks at 86 °F in July, with about 32 days a year at 90 °F or more.

What kind of soil does 52573 have?

The USDA soil survey maps Rinda at the center of ZIP 52573: silty clay loam, poorly drained, pH about 6.2 (slightly acidic).

Did spring come early in Mount Sterling, IA in 2026?

Spring leaf-out near 52573 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 Mount Sterling, IA?

Long-day onions: the longest day near 52573 is 15 h 05 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 52573 change?

Yes. The 2012 USDA map put 52573 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.