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

Planting zone for 72170 — Ulm, AR

ZIP code 72170 (Ulm, Prairie County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is March 11 and the first fall frost November 17.

Where ZIP 72170 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.

Zone8b15 to 20 °F
Coldest night−9.4 to −6.7 °C
Last frostMar 11
First frostNov 17
2012 zone8a

Was 8a 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 8b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Ulm, AR…

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 Ulm, AR

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 11median — 50% chance of a later frost
Safe for tender plantsMarch 31only 10% chance of frost after
First fall frostNovember 17median — 10% chance by Oct 31
Growing season250 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 28 and returns around December 1.

From the NOAA station Stuttgart 9 Ese, AR — 7 miles away, elevation 197 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 72170

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 28 – Feb 11
SpinachSow outdoors · Jan 28 – Feb 18
Broccoli, cabbageStart indoors · Dec 31 – Jan 14
Broccoli, cabbageTransplant · Feb 18 – Mar 4
Onion setsPlant outdoors · Feb 11 – Feb 25
PotatoesPlant outdoors · Feb 18 – Mar 4
LettuceSow outdoors · Feb 11 – Feb 25
Carrots, beetsSow outdoors · Feb 18 – Mar 4
TomatoesStart indoors · Jan 14 – Jan 28
TomatoesTransplant · Mar 18 – Apr 1
Peppers, eggplantStart indoors · Dec 31 – Jan 14
Peppers, eggplantTransplant · Mar 25 – Apr 8
BeansSow outdoors · Mar 18 – Apr 1
Sweet cornSow outdoors · Mar 18 – Apr 1
Cucumbers, squashSow outdoors · Mar 18 – Apr 1
Fall lettuce, spinachSow outdoors · Sep 22 – Oct 6
GarlicPlant cloves · Nov 3 – Dec 8
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 11) and first fall frost (Nov 17) 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 72170 came on Feb 13 — about the same time as the 1991–2020 average (Feb 15).

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 Ulm, AR

The soil mapped at the center of ZIP 72170 is Dewitt — silt loam, poorly drained.

TextureSilt loama good balance for most vegetables
pH5.3strongly acidic; most vegetables like 6.0–7.0
DrainagePoorly drainedconsider raised beds
Organic matter1.75%low — add compost
Hydrologic groupC/Dslow when drained; wet otherwise
Farmland classPrime farmland if drainedUSDA classification

Map unit: Dewitt silt loam, 0 to 1 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 72170; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ulm, AR

Summer high91 °Faverage high, July
Winter low33 °Faverage low, January
Hot days75days a year at 90 °F or more
Freezing nights50nights a year at 32 °F or less
Growing degree days5,652base 50 °F — the season’s usable heat
Longest day14 h 28 mindaylight on June 21
Shortest day9 h 50 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation50.6 inper year, rain and melted snow
Snowfall1 inper year

Average high and low, by month

20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 50 °F, low 33 °F 50°33° JanFebruary: average high 55 °F, low 37 °F 55°37° FebMarch: average high 64 °F, low 44 °F 64°44° MarApril: average high 73 °F, low 53 °F 73°53° AprMay: average high 81 °F, low 63 °F 81°63° MayJune: average high 89 °F, low 71 °F 89°71° JunJuly: average high 91 °F, low 73 °F 91°73° JulAugust: average high 91 °F, low 72 °F 91°72° AugSeptember: average high 86 °F, low 64 °F 86°64° SepOctober: average high 76 °F, low 53 °F 76°53° OctNovember: average high 63 °F, low 43 °F 63°43° NovDecember: average high 53 °F, low 36 °F 53°36° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″4″5″6″January: 3.92 in precipitation, 0.6 in snowfall 3.9❄1 JanFebruary: 4.41 in precipitation, 0.2 in snowfall 4.4 FebMarch: 5.20 in precipitation, 0.4 in snowfall 5.2 MarApril: 5.96 in precipitation 6.0 AprMay: 4.60 in precipitation 4.6 MayJune: 3.66 in precipitation 3.7 JunJuly: 3.23 in precipitation 3.2 JulAugust: 3.19 in precipitation 3.2 AugSeptember: 2.82 in precipitation 2.8 SepOctober: 4.35 in precipitation 4.3 OctNovember: 4.18 in precipitation, 0.1 in snowfall 4.2 NovDecember: 5.11 in precipitation 5.1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Stuttgart 9 Ese, AR (7 mi away); precipitation: Stuttgart 9 Ese, AR (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.

721348b
Roe, AR · 5 mi
720268b
Casscoe, AR · 7 mi
721608b
Stuttgart, AR · 11 mi
720418a
De Valls Bluff, AR · 11 mi
720298a
Clarendon, AR · 12 mi
720388b
Crocketts Bluff, AR · 13 mi
720038b
Almyra, AR · 13 mi
720698b
Holly Grove, AR · 16 mi

Arkansas planting zones →

Questions about 72170

What planting zone is ZIP code 72170?

ZIP code 72170 (Ulm, AR) is in USDA hardiness zone 8b on the 2023 map: the coldest night of an average winter reaches 15 to 20 °F (−9.4 to −6.7 °C).

When is the last frost in Ulm, AR?

The median last spring frost (32 °F) near 72170 is March 11; after March 31 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Stuttgart 9 Ese station.

When is the first frost in Ulm, AR?

The median first fall frost near 72170 is November 17, giving a median frost-free growing season of 250 days.

When should I plant tomatoes in 72170?

Start tomato seeds indoors around Jan 14 – Jan 28 and set transplants outside around Mar 18 – Apr 1, one to three weeks after the median last frost.

How much rain and snow does 72170 get?

About 50.6 inches of precipitation a year and 1 inches of snowfall (NOAA 1991–2020 normals, Stuttgart 9 Ese station).

How hot do summers get in Ulm, AR?

The average high peaks at 91 °F in July, with about 75 days a year at 90 °F or more.

What kind of soil does 72170 have?

The USDA soil survey maps Dewitt at the center of ZIP 72170: silt loam, poorly drained, pH about 5.3 (strongly acidic).

Did spring come early in Ulm, AR in 2026?

Spring leaf-out near 72170 came on Feb 13 in 2026, about the same as the 1991–2020 average (Feb 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ulm, AR?

Intermediate onions: the longest day near 72170 is 14 h 28 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 72170 change?

Yes. The 2012 USDA map put 72170 in zone 8a; the 2023 map puts it in zone 8b. The newer map uses 1991–2020 data and more weather stations.