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

Planting zone for Rock Springs, WY

Rock Springs, WY is in USDA zones 5a to 5b across its 2 ZIP codes. The median last spring frost is May 22 and the first fall frost September 28.

Rock Springs on the zone map

Outlined: its 1 ZIP code areas · 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.

Zones5a–5b−20 to −10 °F
ZIP codes2
Last frostMay 22
First frostSep 28
Growing season126 days

5a 1 ZIP   5b 1 ZIP

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, 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 Rock Springs

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 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 11 mindaylight on June 21
Shortest day9 h 10 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.

ZIP codes in Rock Springs

829015b
−15 to −10 °F
829025a
−20 to −15 °F

Wyoming planting zones →

Questions about Rock Springs

What planting zone is Rock Springs, WY?

Rock Springs, WY is in USDA hardiness zones 5a to 5b on the 2023 map (5a: −20 to −15 °F; 5b: −15 to −10 °F).

When is the last frost in Rock Springs, WY?

The median last spring frost is May 22 and the median first fall frost is September 28 (NOAA 1991–2020 normals, Rock Springs Airport station).

When can I plant a garden in Rock Springs, WY?

Cool-season crops like peas and spinach go in around Apr 10 – May 1; tomatoes, peppers, beans and squash after about May 29, once frost risk has passed.

What kind of onions grow in Rock Springs, WY?

Long-day onions: the longest day is 15 h 11 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

How much rain and snow does Rock Springs, WY get?

About 10.3 inches of precipitation a year (NOAA 1991–2020 normals).