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

Planting zone for 82901 — Rock Springs, WY

ZIP code 82901 (Rock Springs, Sweetwater County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 22 and the first fall frost September 28.

Where ZIP 82901 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.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostMay 22
First frostSep 28
2012 zone5a

Was 5a 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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Rock Springs, 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 Rock Springs, WY

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 22median — 50% chance of a later frost
Safe for tender plantsJune 9only 10% chance of frost after
First fall frostSeptember 28median — 10% chance by Sep 14
Growing season126 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 7 and returns around October 5.

From the NOAA station Rock Springs Airport, WY — 16 miles away, elevation 6,742 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 82901

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 10 – Apr 24
SpinachSow outdoors · Apr 10 – May 1
Broccoli, cabbageStart indoors · Mar 13 – Mar 27
Broccoli, cabbageTransplant · May 1 – May 15
Onion setsPlant outdoors · Apr 24 – May 8
PotatoesPlant outdoors · May 1 – May 15
LettuceSow outdoors · Apr 24 – May 8
Carrots, beetsSow outdoors · May 1 – May 15
TomatoesStart indoors · Mar 27 – Apr 10
TomatoesTransplant · May 29 – Jun 12
Peppers, eggplantStart indoors · Mar 13 – Mar 27
Peppers, eggplantTransplant · Jun 5 – Jun 19
BeansSow outdoors · May 29 – Jun 12
Sweet cornSow outdoors · May 29 – Jun 12
Cucumbers, squashSow outdoors · May 29 – Jun 12
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 22) 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 82901 came on Mar 25 — 30 days earlier than the 1991–2020 average (Apr 24).

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 5b in Wyoming

549 plants native to the lower 48 states, recorded in Wyoming, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. 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 99

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 254

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 162

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 Rock Springs, WY.

Soil in Rock Springs, WY

The soil mapped at the center of ZIP 82901 is Cabbart family — stony silty clay loam, well drained.

TextureStony silty clay loamholds water and nutrients; slow to drain and warm up
pH8.2alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.5%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Cabbart, rubbly surface-Winteridge-Chickenhill, rubbly surface, families, complex, 4 to 35 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 82901; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Rock Springs, WY

Summer high84 °Faverage high, July
Winter low13 °Faverage low, December
Hot days10days a year at 90 °F or more
Freezing nights189nights a year at 32 °F or less
Growing degree days1,914base 50 °F — the season’s usable heat
Longest day15 h 10 mindaylight on June 21
Shortest day9 h 11 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation7.5 inper year, rain and melted snow
Snowfall54 inper year; 69 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 30 °F, low 14 °F 30°14° JanFebruary: average high 33 °F, low 16 °F 33°16° FebMarch: average high 44 °F, low 24 °F 44°24° MarApril: average high 53 °F, low 30 °F 53°30° AprMay: average high 63 °F, low 38 °F 63°38° MayJune: average high 75 °F, low 47 °F 75°47° JunJuly: average high 84 °F, low 55 °F 84°55° JulAugust: average high 82 °F, low 53 °F 82°53° AugSeptember: average high 71 °F, low 44 °F 71°44° SepOctober: average high 56 °F, low 33 °F 56°33° OctNovember: average high 41 °F, low 22 °F 41°22° NovDecember: average high 30 °F, low 13 °F 30°13° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 0.38 in precipitation, 8.2 in snowfall 0.4❄8 JanFebruary: 0.37 in precipitation, 7.9 in snowfall 0.4❄8 FebMarch: 0.58 in precipitation, 6.4 in snowfall 0.6❄6 MarApril: 0.91 in precipitation, 8.8 in snowfall 0.9❄9 AprMay: 1.27 in precipitation, 2.7 in snowfall 1.3❄3 MayJune: 0.70 in precipitation, 0.4 in snowfall 0.7 JunJuly: 0.47 in precipitation 0.5 JulAugust: 0.56 in precipitation 0.6 AugSeptember: 0.79 in precipitation, 1.2 in snowfall 0.8❄1 SepOctober: 0.81 in precipitation, 6.6 in snowfall 0.8❄7 OctNovember: 0.40 in precipitation, 6 in snowfall 0.4❄6 NovDecember: 0.31 in precipitation, 5.8 in snowfall 0.3❄6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Rock Springs Airport, WY (16 mi away); precipitation: Rock Springs Airport, WY (16 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

7 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

829025a
Rock Springs, WY · 19 mi
829455a
Superior, WY · 24 mi
829435a
Reliance, WY · 25 mi
829425a
Point Of Rocks, WY · 25 mi
840235b
Dutch John, UT · 35 mi
829355a
Green River, WY · 41 mi
823364b
Wamsutter, WY · 46 mi
816406a
Maybell, CO · 55 mi

All 2 ZIP codes in Rock Springs → · Wyoming planting zones →

Questions about 82901

What planting zone is ZIP code 82901?

ZIP code 82901 (Rock Springs, WY) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Rock Springs, WY?

The median last spring frost (32 °F) near 82901 is May 22; after June 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Rock Springs Airport station.

When is the first frost in Rock Springs, WY?

The median first fall frost near 82901 is September 28, giving a median frost-free growing season of 126 days.

When should I plant tomatoes in 82901?

Start tomato seeds indoors around Mar 27 – Apr 10 and set transplants outside around May 29 – Jun 12, one to three weeks after the median last frost.

How much rain and snow does 82901 get?

About 7.5 inches of precipitation a year and 54 inches of snowfall (NOAA 1991–2020 normals, Rock Springs Airport station).

How hot do summers get in Rock Springs, WY?

The average high peaks at 84 °F in July, with about 10 days a year at 90 °F or more.

What kind of soil does 82901 have?

The USDA soil survey maps Cabbart family at the center of ZIP 82901: stony silty clay loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Rock Springs, WY in 2026?

Spring leaf-out near 82901 came on Mar 25 in 2026, 30 days earlier than the 1991–2020 average (Apr 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Rock Springs, WY?

Long-day onions: the longest day near 82901 is 15 h 10 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 82901 change?

Yes. The 2012 USDA map put 82901 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.