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

Planting zone for 82501 — Riverton, WY

ZIP code 82501 (Riverton, Fremont County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 12 and the first fall frost September 24.

Where ZIP 82501 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 12
First frostSep 24
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 Riverton, 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 Riverton, WY

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 12median — 50% chance of a later frost
Safe for tender plantsMay 26only 10% chance of frost after
First fall frostSeptember 24median — 10% chance by Sep 11
Growing season132 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 1 and returns around October 4.

From the NOAA station Riverton, WY — 7 miles away, elevation 4,954 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 82501

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 31 – Apr 14
SpinachSow outdoors · Mar 31 – Apr 21
Broccoli, cabbageStart indoors · Mar 3 – Mar 17
Broccoli, cabbageTransplant · Apr 21 – May 5
Onion setsPlant outdoors · Apr 14 – Apr 28
PotatoesPlant outdoors · Apr 21 – May 5
LettuceSow outdoors · Apr 14 – Apr 28
Carrots, beetsSow outdoors · Apr 21 – May 5
TomatoesStart indoors · Mar 17 – Mar 31
TomatoesTransplant · May 19 – Jun 2
Peppers, eggplantStart indoors · Mar 3 – Mar 17
Peppers, eggplantTransplant · May 26 – Jun 9
BeansSow outdoors · May 19 – Jun 2
Sweet cornSow outdoors · May 19 – Jun 2
Cucumbers, squashSow outdoors · May 19 – Jun 2
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 12) 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 82501 came on Mar 19 — 22 days earlier than the 1991–2020 average (Apr 10).

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 Riverton, WY.

Soil in Riverton, WY

The soil mapped at the center of ZIP 82501 is Oceanet — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH8.5alkaline; 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: Oceanet-Persayo-Rock outcrop complex, 6 to 45 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 82501; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Riverton, WY

Summer high88 °Faverage high, July
Winter low4 °Faverage low, January
Hot days38days a year at 90 °F or more
Freezing nights193nights a year at 32 °F or less
Growing degree days2,218base 50 °F — the season’s usable heat
Longest day15 h 22 mindaylight on June 21
Shortest day9 h 00 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation9.5 inper year, rain and melted snow
Snowfall44 inper year; 76 days with snow on the ground

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 29 °F, low 4 °F 29°4° JanFebruary: average high 36 °F, low 10 °F 36°10° FebMarch: average high 49 °F, low 22 °F 49°22° MarApril: average high 58 °F, low 31 °F 58°31° AprMay: average high 67 °F, low 40 °F 67°40° MayJune: average high 79 °F, low 49 °F 79°49° JunJuly: average high 88 °F, low 55 °F 88°55° JulAugust: average high 86 °F, low 52 °F 86°52° AugSeptember: average high 74 °F, low 43 °F 74°43° SepOctober: average high 59 °F, low 30 °F 59°30° OctNovember: average high 43 °F, low 17 °F 43°17° NovDecember: average high 30 °F, low 6 °F 30°6° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 0.35 in precipitation, 5.5 in snowfall 0.3❄6 JanFebruary: 0.43 in precipitation, 7.4 in snowfall 0.4❄7 FebMarch: 0.71 in precipitation, 6.5 in snowfall 0.7❄7 MarApril: 1.31 in precipitation, 7.2 in snowfall 1.3❄7 AprMay: 1.98 in precipitation, 2.1 in snowfall 2.0❄2 MayJune: 1.09 in precipitation 1.1 JunJuly: 0.70 in precipitation 0.7 JulAugust: 0.45 in precipitation 0.5 AugSeptember: 0.80 in precipitation, 0.6 in snowfall 0.8❄1 SepOctober: 0.93 in precipitation, 4.4 in snowfall 0.9❄4 OctNovember: 0.44 in precipitation, 5.3 in snowfall 0.4❄5 NovDecember: 0.31 in precipitation, 5.3 in snowfall 0.3❄5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Riverton, WY (7 mi away); precipitation: Riverton, WY (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

825244b
Saint Stephens, WY · 10 mi
825105a
Arapahoe, WY · 19 mi
825155a
Hudson, WY · 19 mi
826494b
Shoshoni, WY · 21 mi
825165a
Kinnear, WY · 32 mi
825205a
Lander, WY · 32 mi
826425a
Lysite, WY · 34 mi
825235a
Pavillion, WY · 41 mi

Wyoming planting zones →

Questions about 82501

What planting zone is ZIP code 82501?

ZIP code 82501 (Riverton, 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 Riverton, WY?

The median last spring frost (32 °F) near 82501 is May 12; after May 26 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Riverton station.

When is the first frost in Riverton, WY?

The median first fall frost near 82501 is September 24, giving a median frost-free growing season of 132 days.

When should I plant tomatoes in 82501?

Start tomato seeds indoors around Mar 17 – Mar 31 and set transplants outside around May 19 – Jun 2, one to three weeks after the median last frost.

How much rain and snow does 82501 get?

About 9.5 inches of precipitation a year and 44 inches of snowfall (NOAA 1991–2020 normals, Riverton station).

How hot do summers get in Riverton, WY?

The average high peaks at 88 °F in July, with about 38 days a year at 90 °F or more.

What kind of soil does 82501 have?

The USDA soil survey maps Oceanet at the center of ZIP 82501: sandy loam, well drained, pH about 8.5 (alkaline).

Did spring come early in Riverton, WY in 2026?

Spring leaf-out near 82501 came on Mar 19 in 2026, 22 days earlier than the 1991–2020 average (Apr 10), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Riverton, WY?

Long-day onions: the longest day near 82501 is 15 h 22 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 82501 change?

Yes. The 2012 USDA map put 82501 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.