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

Planting zone for 82620 — Alcova, WY

ZIP code 82620 (Alcova, Natrona County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 9 and the first fall frost October 7.

Where ZIP 82620 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 9
First frostOct 7
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 Alcova, 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 Alcova, WY

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 9median — 50% chance of a later frost
Safe for tender plantsMay 23only 10% chance of frost after
First fall frostOctober 7median — 10% chance by Sep 22
Growing season148 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 30 and returns around October 16.

From the NOAA station Pathfinder Dam, WY — 12 miles away, elevation 5,922 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 82620

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 28 – Apr 11
SpinachSow outdoors · Mar 28 – Apr 18
Broccoli, cabbageStart indoors · Feb 28 – Mar 14
Broccoli, cabbageTransplant · Apr 18 – May 2
Onion setsPlant outdoors · Apr 11 – Apr 25
PotatoesPlant outdoors · Apr 18 – May 2
LettuceSow outdoors · Apr 11 – Apr 25
Carrots, beetsSow outdoors · Apr 18 – May 2
TomatoesStart indoors · Mar 14 – Mar 28
TomatoesTransplant · May 16 – May 30
Peppers, eggplantStart indoors · Feb 28 – Mar 14
Peppers, eggplantTransplant · May 23 – Jun 6
BeansSow outdoors · May 16 – May 30
Sweet cornSow outdoors · May 16 – May 30
Cucumbers, squashSow outdoors · May 16 – May 30
Fall lettuce, spinachSow outdoors · Aug 12 – Aug 26
GarlicPlant cloves · Sep 23 – Oct 28
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 9) and first fall frost (Oct 7) 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 82620 came on Mar 20 — 26 days earlier than the 1991–2020 average (Apr 15).

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 Alcova, WY.

Soil in Alcova, WY

The soil mapped at the center of ZIP 82620 is Aquic Ustifluvents — slightly decomposed plant material, poorly drained.

TextureSlightly decomposed plant materialtop layer
DrainagePoorly drainedconsider raised beds
Organic matter85%high
Hydrologic groupA/Ddrains fast once dried out; wet otherwise
Farmland classNot prime farmlandUSDA classification

Map unit: Aquic Ustifluvents, saline, 0 to 3 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 82620; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Alcova, WY

Summer high86 °Faverage high, July
Winter low16 °Faverage low, January
Hot days16days a year at 90 °F or more
Freezing nights158nights a year at 32 °F or less
Growing degree days2,288base 50 °F — the season’s usable heat
Longest day15 h 18 mindaylight on June 21
Shortest day9 h 03 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation11.2 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 33 °F, low 16 °F 33°16° JanFebruary: average high 36 °F, low 17 °F 36°17° FebMarch: average high 46 °F, low 26 °F 46°26° MarApril: average high 54 °F, low 32 °F 54°32° AprMay: average high 64 °F, low 41 °F 64°41° MayJune: average high 77 °F, low 50 °F 77°50° JunJuly: average high 86 °F, low 58 °F 86°58° JulAugust: average high 83 °F, low 57 °F 83°57° AugSeptember: average high 73 °F, low 48 °F 73°48° SepOctober: average high 58 °F, low 36 °F 58°36° OctNovember: average high 45 °F, low 27 °F 45°27° NovDecember: average high 33 °F, low 18 °F 33°18° Dec

Precipitation by month inches

0″1″2″January: 0.58 in precipitation 0.6 JanFebruary: 0.48 in precipitation 0.5 FebMarch: 0.83 in precipitation 0.8 MarApril: 1.24 in precipitation 1.2 AprMay: 1.93 in precipitation 1.9 MayJune: 1.37 in precipitation 1.4 JunJuly: 0.74 in precipitation 0.7 JulAugust: 1.05 in precipitation 1.1 AugSeptember: 0.83 in precipitation 0.8 SepOctober: 1.13 in precipitation 1.1 OctNovember: 0.49 in precipitation 0.5 NovDecember: 0.53 in precipitation 0.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Pathfinder Dam, WY (12 mi away); precipitation: Pathfinder Dam, WY (12 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

826045a
Casper, WY · 32 mi
823225b
Bairoil, WY · 32 mi
826465a
Natrona, WY · 34 mi
823275a
Hanna, WY · 35 mi
826385a
Hiland, WY · 37 mi
826485a
Powder River, WY · 39 mi
823345a
Sinclair, WY · 41 mi
826445a
Mills, WY · 41 mi

Wyoming planting zones →

Questions about 82620

What planting zone is ZIP code 82620?

ZIP code 82620 (Alcova, 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 Alcova, WY?

The median last spring frost (32 °F) near 82620 is May 9; after May 23 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Pathfinder Dam station.

When is the first frost in Alcova, WY?

The median first fall frost near 82620 is October 7, giving a median frost-free growing season of 148 days.

When should I plant tomatoes in 82620?

Start tomato seeds indoors around Mar 14 – Mar 28 and set transplants outside around May 16 – May 30, one to three weeks after the median last frost.

How much rain and snow does 82620 get?

About 11.2 inches of precipitation a year (NOAA 1991–2020 normals, Pathfinder Dam station).

How hot do summers get in Alcova, WY?

The average high peaks at 86 °F in July, with about 16 days a year at 90 °F or more.

What kind of soil does 82620 have?

The USDA soil survey maps Aquic Ustifluvents at the center of ZIP 82620: slightly decomposed plant material, poorly drained.

Did spring come early in Alcova, WY in 2026?

Spring leaf-out near 82620 came on Mar 20 in 2026, 26 days earlier than the 1991–2020 average (Apr 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Alcova, WY?

Long-day onions: the longest day near 82620 is 15 h 18 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).