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

Planting zone for 82902 — Rock Springs, WY

ZIP code 82902 (Rock Springs, Sweetwater County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 24 and the first fall frost September 24.

Where ZIP 82902 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 24
First frostSep 24
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 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 24median — 50% chance of a later frost
Safe for tender plantsJune 9only 10% chance of frost after
First fall frostSeptember 24median — 10% chance by Sep 9
Growing season121 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 9 and returns around October 3.

From the NOAA station Rock Springs Fire Dept, WY — 2 miles away, elevation 6,270 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 82902

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 12 – Apr 26
SpinachSow outdoors · Apr 12 – May 3
Broccoli, cabbageStart indoors · Mar 15 – Mar 29
Broccoli, cabbageTransplant · May 3 – May 17
Onion setsPlant outdoors · Apr 26 – May 10
PotatoesPlant outdoors · May 3 – May 17
LettuceSow outdoors · Apr 26 – May 10
Carrots, beetsSow outdoors · May 3 – May 17
TomatoesStart indoors · Mar 29 – Apr 12
TomatoesTransplant · May 31 – Jun 14
Peppers, eggplantStart indoors · Mar 15 – Mar 29
Peppers, eggplantTransplant · Jun 7 – Jun 21
BeansSow outdoors · May 31 – Jun 14
Sweet cornSow outdoors · May 31 – Jun 14
Cucumbers, squashSow outdoors · May 31 – Jun 14
Fall lettuce, spinachSow outdoors · Jul 30 – Aug 13
GarlicPlant cloves · Sep 10 – Oct 15
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 24) and first fall frost (Sep 24) 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 82902 came on Mar 25 — 24 days earlier than the 1991–2020 average (Apr 18).

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 Rock Springs, WY.

Soil in Rock Springs, WY

The soil mapped at the center of ZIP 82902 is Blackhall — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH8.0alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Blackhall-Cryluha-Edlin complex, 2 to 8 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 82902; 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 high86 °Faverage high, July
Winter low12 °Faverage low, January
Hot days15days a year at 90 °F or more
Freezing nights184nights a year at 32 °F or less
Growing degree days1,970base 50 °F — the season’s usable heat
Longest day15 h 12 mindaylight on June 21
Shortest day9 h 09 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation10.3 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 35 °F, low 12 °F 35°12° JanFebruary: average high 38 °F, low 15 °F 38°15° FebMarch: average high 49 °F, low 23 °F 49°23° MarApril: average high 57 °F, low 30 °F 57°30° AprMay: average high 67 °F, low 37 °F 67°37° MayJune: average high 79 °F, low 45 °F 79°45° JunJuly: average high 86 °F, low 53 °F 86°53° JulAugust: average high 84 °F, low 51 °F 84°51° AugSeptember: average high 75 °F, low 41 °F 75°41° SepOctober: average high 61 °F, low 31 °F 61°31° OctNovember: average high 45 °F, low 21 °F 45°21° NovDecember: average high 33 °F, low 12 °F 33°12° Dec

Precipitation by month inches

0″1″2″January: 0.41 in precipitation 0.4 JanFebruary: 0.63 in precipitation 0.6 FebMarch: 0.60 in precipitation 0.6 MarApril: 1.14 in precipitation 1.1 AprMay: 1.74 in precipitation 1.7 MayJune: 0.83 in precipitation 0.8 JunJuly: 0.94 in precipitation 0.9 JulAugust: 0.73 in precipitation 0.7 AugSeptember: 1.03 in precipitation 1.0 SepOctober: 0.93 in precipitation 0.9 OctNovember: 0.63 in precipitation 0.6 NovDecember: 0.64 in precipitation 0.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Rock Springs Fire Dept, WY (2 mi away); precipitation: Rock Springs 0.9 S, WY (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

829435a
Reliance, WY · 8 mi
829455a
Superior, WY · 16 mi
829015b
Rock Springs, WY · 19 mi
829425a
Point Of Rocks, WY · 24 mi
829355a
Green River, WY · 24 mi
829295a
Little America, WY · 35 mi
829324a
Farson, WY · 38 mi
829344b
Granger, WY · 41 mi

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

Questions about 82902

What planting zone is ZIP code 82902?

ZIP code 82902 (Rock Springs, 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 Rock Springs, WY?

The median last spring frost (32 °F) near 82902 is May 24; after June 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Rock Springs Fire Dept station.

When is the first frost in Rock Springs, WY?

The median first fall frost near 82902 is September 24, giving a median frost-free growing season of 121 days.

When should I plant tomatoes in 82902?

Start tomato seeds indoors around Mar 29 – Apr 12 and set transplants outside around May 31 – Jun 14, one to three weeks after the median last frost.

How much rain and snow does 82902 get?

About 10.3 inches of precipitation a year (NOAA 1991–2020 normals, Rock Springs 0.9 S station).

How hot do summers get in Rock Springs, WY?

The average high peaks at 86 °F in July, with about 15 days a year at 90 °F or more.

What kind of soil does 82902 have?

The USDA soil survey maps Blackhall at the center of ZIP 82902: sandy loam, well drained, pH about 8.0 (alkaline).

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

Spring leaf-out near 82902 came on Mar 25 in 2026, 24 days earlier than the 1991–2020 average (Apr 18), 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 82902 is 15 h 12 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).