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

Planting zone for 82601 — Casper, WY

ZIP code 82601 (Casper, Natrona County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 26 and the first fall frost September 22.

Where ZIP 82601 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 26
First frostSep 22
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 Casper, 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 Casper, WY

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 26median — 50% chance of a later frost
Safe for tender plantsJune 10only 10% chance of frost after
First fall frostSeptember 22median — 10% chance by Sep 5
Growing season117 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 11 and returns around October 2.

From the NOAA station Casper Natrona Co. Airport, WY — 14 miles away, elevation 5,338 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 82601

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 14 – Apr 28
SpinachSow outdoors · Apr 14 – May 5
Broccoli, cabbageStart indoors · Mar 17 – Mar 31
Broccoli, cabbageTransplant · May 5 – May 19
Onion setsPlant outdoors · Apr 28 – May 12
PotatoesPlant outdoors · May 5 – May 19
LettuceSow outdoors · Apr 28 – May 12
Carrots, beetsSow outdoors · May 5 – May 19
TomatoesStart indoors · Mar 31 – Apr 14
TomatoesTransplant · Jun 2 – Jun 16
Peppers, eggplantStart indoors · Mar 17 – Mar 31
Peppers, eggplantTransplant · Jun 9 – Jun 23
BeansSow outdoors · Jun 2 – Jun 16
Sweet cornSow outdoors · Jun 2 – Jun 16
Cucumbers, squashSow outdoors · Jun 2 – Jun 16
Fall lettuce, spinachSow outdoors · Jul 28 – Aug 11
GarlicPlant cloves · Sep 8 – Oct 13
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 26) and first fall frost (Sep 22) 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 82601 came on Mar 18 — 28 days earlier than the 1991–2020 average (Apr 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).

Native plants for zone 5a in Wyoming

542 plants native to the lower 48 states, recorded in Wyoming, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. Each links to its USDA PLANTS profile.

Trees 22

American elm120 ft · blooms early spring · medium shade tolerance · to −46 °Fbalsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fblue spruce100 ft · blooms late spring · medium shade tolerance · to −38 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °FDouglas-fir200 ft · blooms mid spring · medium shade tolerance · to −33 °F

Shrubs 98

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °Falderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °F

Wildflowers & perennials 249

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °Falpine sweetvetch2 ft · blooms early summer · high shade tolerance · to −62 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °F

Grasses 161

Alaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °FAlpine Meadow-Foxtail0.5 ft · blooms mid spring · medium shade tolerance · to −33 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Fanalogue sedge1.5 ft · blooms late spring · medium shade tolerance · to −38 °F

Vines 3

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Fwestern white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °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 Casper, WY.

Soil in Casper, WY

The soil mapped at the center of ZIP 82601 is Zigweid — loam, well drained.

TextureLoama good balance for most vegetables
pH7.9alkaline; 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 importance, if irrigatedUSDA classification

Map unit: Zigweid-Theedle loams, 3 to 15 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 82601; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Casper, WY

Summer high89 °Faverage high, July
Winter low15 °Faverage low, January
Hot days38days a year at 90 °F or more
Freezing nights183nights a year at 32 °F or less
Growing degree days2,156base 50 °F — the season’s usable heat
Longest day15 h 22 mindaylight on June 21
Shortest day9 h 00 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation12.2 inper year, rain and melted snow
Snowfall72 inper year; 64 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 35 °F, low 15 °F 35°15° JanFebruary: average high 38 °F, low 15 °F 38°15° FebMarch: average high 49 °F, low 23 °F 49°23° MarApril: average high 56 °F, low 28 °F 56°28° AprMay: average high 67 °F, low 37 °F 67°37° MayJune: average high 80 °F, low 45 °F 80°45° JunJuly: average high 89 °F, low 53 °F 89°53° JulAugust: average high 87 °F, low 51 °F 87°51° AugSeptember: average high 76 °F, low 42 °F 76°42° SepOctober: average high 60 °F, low 31 °F 60°31° OctNovember: average high 46 °F, low 22 °F 46°22° NovDecember: average high 35 °F, low 15 °F 35°15° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″January: 0.49 in precipitation, 9 in snowfall 0.5❄9 JanFebruary: 0.56 in precipitation, 10.9 in snowfall 0.6❄11 FebMarch: 0.84 in precipitation, 10.3 in snowfall 0.8❄10 MarApril: 1.41 in precipitation, 10.5 in snowfall 1.4❄11 AprMay: 2.21 in precipitation, 2.6 in snowfall 2.2❄3 MayJune: 1.34 in precipitation, 0.1 in snowfall 1.3 JunJuly: 1.19 in precipitation 1.2 JulAugust: 0.79 in precipitation 0.8 AugSeptember: 0.95 in precipitation, 1.5 in snowfall 0.9❄2 SepOctober: 1.19 in precipitation, 7 in snowfall 1.2❄7 OctNovember: 0.64 in precipitation, 8.9 in snowfall 0.6❄9 NovDecember: 0.61 in precipitation, 11 in snowfall 0.6❄11 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Casper Natrona Co. Airport, WY (14 mi away); precipitation: Casper Natrona Co. Airport, WY (14 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

826025a
Casper, WY · 12 mi
826055a
Casper, WY · 14 mi
826445a
Mills, WY · 16 mi
826365a
Evansville, WY · 19 mi
826045a
Casper, WY · 21 mi
826095a
Casper, WY · 22 mi
826465a
Natrona, WY · 22 mi
826435a
Midwest, WY · 25 mi

All 5 ZIP codes in Casper → · Wyoming planting zones →

Questions about 82601

What planting zone is ZIP code 82601?

ZIP code 82601 (Casper, WY) 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 Casper, WY?

The median last spring frost (32 °F) near 82601 is May 26; after June 10 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Casper Natrona Co. Airport station.

When is the first frost in Casper, WY?

The median first fall frost near 82601 is September 22, giving a median frost-free growing season of 117 days.

When should I plant tomatoes in 82601?

Start tomato seeds indoors around Mar 31 – Apr 14 and set transplants outside around Jun 2 – Jun 16, one to three weeks after the median last frost.

How much rain and snow does 82601 get?

About 12.2 inches of precipitation a year and 72 inches of snowfall (NOAA 1991–2020 normals, Casper Natrona Co. Airport station).

How hot do summers get in Casper, WY?

The average high peaks at 89 °F in July, with about 38 days a year at 90 °F or more.

What kind of soil does 82601 have?

The USDA soil survey maps Zigweid at the center of ZIP 82601: loam, well drained, pH about 7.9 (alkaline).

Did spring come early in Casper, WY in 2026?

Spring leaf-out near 82601 came on Mar 18 in 2026, 28 days earlier than the 1991–2020 average (Apr 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Casper, WY?

Long-day onions: the longest day near 82601 is 15 h 22 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).