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

Planting zone for 82833 — Big Horn, WY

ZIP code 82833 (Big Horn, Sheridan County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 17 and the first fall frost September 28.

Where ZIP 82833 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 17

First frostSep 28

2012 zone4b

Was 4b 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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Big Horn, 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 Big Horn, WY

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 17median — 50% chance of a later frost

Safe for tender plantsMay 31only 10% chance of frost after

First fall frostSeptember 28median — 10% chance by Sep 13

Growing season132 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 5.

From the NOAA station Big Horn, WY — 9 miles away, elevation 4,210 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 82833

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 5 – Apr 19

SpinachSow outdoors · Apr 5 – Apr 26

Broccoli, cabbageStart indoors · Mar 8 – Mar 22

Broccoli, cabbageTransplant · Apr 26 – May 10

Onion setsPlant outdoors · Apr 19 – May 3

PotatoesPlant outdoors · Apr 26 – May 10

LettuceSow outdoors · Apr 19 – May 3

Carrots, beetsSow outdoors · Apr 26 – May 10

TomatoesStart indoors · Mar 22 – Apr 5

TomatoesTransplant · May 24 – Jun 7

Peppers, eggplantStart indoors · Mar 8 – Mar 22

Peppers, eggplantTransplant · May 31 – Jun 14

BeansSow outdoors · May 24 – Jun 7

Sweet cornSow outdoors · May 24 – Jun 7

Cucumbers, squashSow outdoors · May 24 – Jun 7

Fall lettuce, spinachSow outdoors · Aug 3 – Aug 17

GarlicPlant cloves · Sep 14 – Oct 19

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 17) and first fall frost (Sep 28) 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 82833 came on May 7 — about the same time as the 1991–2020 average (May 6).

average
May 62026
May 7

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 Big Horn, WY.

Soil in Big Horn, WY

The soil mapped at the center of ZIP 82833 is Tellman — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer

pH5.0strongly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter75%high

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Tellman-Granile-Agneston association, 2 to 20 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 82833; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Big Horn, WY

Summer high84 °Faverage high, July

Winter low14 °Faverage low, December

Hot days23days a year at 90 °F or more

Freezing nights177nights a year at 32 °F or less

Growing degree days2,082base 50 °F — the season’s usable heat

Longest day15 h 34 mindaylight on June 21

Shortest day8 h 49 mindaylight on December 21

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

Precipitation25 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: Big Horn, WY (9 mi away); precipitation: Big Goose, WY (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

Saddlestring, WY · 16 mi

Ranchester, WY · 25 mi

Wyoming planting zones →

Questions about 82833

What planting zone is ZIP code 82833?

ZIP code 82833 (Big Horn, 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 Big Horn, WY?

The median last spring frost (32 °F) near 82833 is May 17; after May 31 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Big Horn station.

When is the first frost in Big Horn, WY?

The median first fall frost near 82833 is September 28, giving a median frost-free growing season of 132 days.

When should I plant tomatoes in 82833?

Start tomato seeds indoors around Mar 22 – Apr 5 and set transplants outside around May 24 – Jun 7, one to three weeks after the median last frost.

How much rain and snow does 82833 get?

About 25 inches of precipitation a year (NOAA 1991–2020 normals, Big Goose station).

How hot do summers get in Big Horn, WY?

The average high peaks at 84 °F in July, with about 23 days a year at 90 °F or more.

What kind of soil does 82833 have?

The USDA soil survey maps Tellman at the center of ZIP 82833: slightly decomposed plant material, well drained, pH about 5.0 (strongly acidic).

Did spring come early in Big Horn, WY in 2026?

Spring leaf-out near 82833 came on May 7 in 2026, about the same as the 1991–2020 average (May 6), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Big Horn, WY?

Long-day onions: the longest day near 82833 is 15 h 34 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 82833 change?

Yes. The 2012 USDA map put 82833 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.