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

Planting zone for 82602 — Casper, WY

ZIP code 82602 (Casper, Natrona County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 10 and the first fall frost September 29.

Where ZIP 82602 is

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 10

First frostSep 29

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 10median — 50% chance of a later frost

Safe for tender plantsMay 24only 10% chance of frost after

First fall frostSeptember 29median — 10% chance by Sep 14

Growing season138 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 1 and returns around October 6.

From the NOAA station Casper Wwtp, WY — 4 miles away, elevation 5,099 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 82602

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 29 – Apr 12

SpinachSow outdoors · Mar 29 – Apr 19

Broccoli, cabbageStart indoors · Mar 1 – Mar 15

Broccoli, cabbageTransplant · Apr 19 – May 3

Onion setsPlant outdoors · Apr 12 – Apr 26

PotatoesPlant outdoors · Apr 19 – May 3

LettuceSow outdoors · Apr 12 – Apr 26

Carrots, beetsSow outdoors · Apr 19 – May 3

TomatoesStart indoors · Mar 15 – Mar 29

TomatoesTransplant · May 17 – May 31

Peppers, eggplantStart indoors · Mar 1 – Mar 15

Peppers, eggplantTransplant · May 24 – Jun 7

BeansSow outdoors · May 17 – May 31

Sweet cornSow outdoors · May 17 – May 31

Cucumbers, squashSow outdoors · May 17 – May 31

Fall lettuce, spinachSow outdoors · Aug 4 – Aug 18

GarlicPlant cloves · Sep 15 – Oct 20

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 10) and first fall frost (Sep 29) 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 82602 came on Mar 3 — 37 days earlier than the 1991–2020 average (Apr 9).

average
Apr 92026
Mar 3

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.

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 82602 is Hiland — loamy sand, well drained.

TextureLoamy sanddrains and warms fast; dries out and needs more feeding

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Hiland loamy sand, 2 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 82602; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Casper, WY

Summer high88 °Faverage high, July

Winter low17 °Faverage low, January

Hot days36days a year at 90 °F or more

Freezing nights163nights a year at 32 °F or less

Growing degree days2,405base 50 °F — the season’s usable heat

Longest day15 h 21 mindaylight on June 21

Shortest day9 h 01 mindaylight on December 21

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

Precipitation13.4 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: Casper Wwtp, WY (4 mi away); precipitation: Casper Wwtp, WY (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

Evansville, WY · 11 mi

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

Questions about 82602

What planting zone is ZIP code 82602?

ZIP code 82602 (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 82602 is May 10; after May 24 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Casper Wwtp station.

When is the first frost in Casper, WY?

The median first fall frost near 82602 is September 29, giving a median frost-free growing season of 138 days.

When should I plant tomatoes in 82602?

Start tomato seeds indoors around Mar 15 – Mar 29 and set transplants outside around May 17 – May 31, one to three weeks after the median last frost.

How much rain and snow does 82602 get?

About 13.4 inches of precipitation a year (NOAA 1991–2020 normals, Casper Wwtp station).

How hot do summers get in Casper, WY?

The average high peaks at 88 °F in July, with about 36 days a year at 90 °F or more.

What kind of soil does 82602 have?

The USDA soil survey maps Hiland at the center of ZIP 82602: loamy sand, well drained, pH about 7.0 (neutral).

Did spring come early in Casper, WY in 2026?

Spring leaf-out near 82602 came on Mar 3 in 2026, 37 days earlier than the 1991–2020 average (Apr 9), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Casper, WY?

Long-day onions: the longest day near 82602 is 15 h 21 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).