Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 82721 — Moorcroft, WY

ZIP code 82721 (Moorcroft, Crook County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 23 and the first fall frost September 20.

Where ZIP 82721 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.

Zone4b−25 to −20 °F

Coldest night−31.7 to −28.9 °C

Last frostMay 23

First frostSep 20

2012 zone4a

Was 4a 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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Moorcroft, WY…

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 Moorcroft, WY

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 23median — 50% chance of a later frost

Safe for tender plantsJune 6only 10% chance of frost after

First fall frostSeptember 20median — 10% chance by Sep 4

Growing season118 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 12 and returns around October 1.

From the NOAA station Devils Twr #2, WY — 12 miles away, elevation 3,862 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 82721

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 11 – Apr 25

SpinachSow outdoors · Apr 11 – May 2

Broccoli, cabbageStart indoors · Mar 14 – Mar 28

Broccoli, cabbageTransplant · May 2 – May 16

Onion setsPlant outdoors · Apr 25 – May 9

PotatoesPlant outdoors · May 2 – May 16

LettuceSow outdoors · Apr 25 – May 9

Carrots, beetsSow outdoors · May 2 – May 16

TomatoesStart indoors · Mar 28 – Apr 11

TomatoesTransplant · May 30 – Jun 13

Peppers, eggplantStart indoors · Mar 14 – Mar 28

Peppers, eggplantTransplant · Jun 6 – Jun 20

BeansSow outdoors · May 30 – Jun 13

Sweet cornSow outdoors · May 30 – Jun 13

Cucumbers, squashSow outdoors · May 30 – Jun 13

Fall lettuce, spinachSow outdoors · Jul 26 – Aug 9

GarlicPlant cloves · Sep 6 – Oct 11

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 23) and first fall frost (Sep 20) 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 82721 came on Mar 23 — 21 days earlier than the 1991–2020 average (Apr 13).

average
Apr 132026
Mar 23

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 4b in Wyoming

495 plants native to the lower 48 states, recorded in Wyoming, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. Each links to its USDA PLANTS profile.

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 Moorcroft, WY.

Soil in Moorcroft, WY

The soil mapped at the center of ZIP 82721 is Louviers — clay, well drained.

TextureClayholds water and nutrients; slow to drain and warm up

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Louviers-Grummit complex, 10 to 30 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 82721; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Moorcroft, WY

Summer high85 °Faverage high, July

Winter low8 °Faverage low, January

Hot days25days a year at 90 °F or more

Freezing nights201nights a year at 32 °F or less

Growing degree days2,120base 50 °F — the season’s usable heat

Longest day15 h 33 mindaylight on June 21

Shortest day8 h 50 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation19.2 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Devils Twr #2, WY (12 mi away); precipitation: Carlile 6.7 Ene, WY (12 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.

827144b

Devils Tower, WY · 13 mi

Wyoming planting zones →

Questions about 82721

What planting zone is ZIP code 82721?

ZIP code 82721 (Moorcroft, WY) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Moorcroft, WY?

The median last spring frost (32 °F) near 82721 is May 23; after June 6 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Devils Twr #2 station.

When is the first frost in Moorcroft, WY?

The median first fall frost near 82721 is September 20, giving a median frost-free growing season of 118 days.

When should I plant tomatoes in 82721?

Start tomato seeds indoors around Mar 28 – Apr 11 and set transplants outside around May 30 – Jun 13, one to three weeks after the median last frost.

How much rain and snow does 82721 get?

About 19.2 inches of precipitation a year (NOAA 1991–2020 normals, Carlile 6.7 Ene station).

How hot do summers get in Moorcroft, WY?

The average high peaks at 85 °F in July, with about 25 days a year at 90 °F or more.

What kind of soil does 82721 have?

The USDA soil survey maps Louviers at the center of ZIP 82721: clay, well drained, pH about 7.0 (neutral).

Did spring come early in Moorcroft, WY in 2026?

Spring leaf-out near 82721 came on Mar 23 in 2026, 21 days earlier than the 1991–2020 average (Apr 13), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Moorcroft, WY?

Long-day onions: the longest day near 82721 is 15 h 33 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 82721 change?

Yes. The 2012 USDA map put 82721 in zone 4a; the 2023 map puts it in zone 4b. The newer map uses 1991–2020 data and more weather stations.