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

Planting zone for 82434 — Otto, WY

ZIP code 82434 (Otto, Big Horn County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is May 12 and the first fall frost September 28.

Where ZIP 82434 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.

Zone4b−25 to −20 °F
Coldest night−31.7 to −28.9 °C
Last frostMay 12
First frostSep 28
2012 zone4b

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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Otto, 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 Otto, 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 27only 10% chance of frost after
First fall frostSeptember 28median — 10% chance by Sep 14
Growing season136 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 1 and returns around October 7.

From the NOAA station Emblem, WY — 11 miles away, elevation 4,449 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 82434

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 · 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 12) 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 82434 came on Mar 21 — 18 days earlier than the 1991–2020 average (Apr 8).

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 4b in Wyoming

495 plants native to the lower 48 states, recorded in Wyoming, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. 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 83

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 226

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 152

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 Otto, WY.

Soil in Otto, WY

The soil mapped at the center of ZIP 82434 is Bributte — clay, well drained.

TextureClayholds water and nutrients; slow to drain and warm up
pH8.4alkaline; 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: Bributte-Persayo-Pavillion complex, 3 to 60 percent slopes -- Draft.

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 82434; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Otto, WY

Summer high86 °Faverage high, July
Winter low9 °Faverage low, January
Hot days28days a year at 90 °F or more
Freezing nights181nights a year at 32 °F or less
Growing degree days2,183base 50 °F — the season’s usable heat
Longest day15 h 32 mindaylight on June 21
Shortest day8 h 51 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation7.7 inper year, rain and melted snow
Snowfall16 inper year; 14 days with snow on the ground

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 31 °F, low 9 °F 31°9° JanFebruary: average high 35 °F, low 13 °F 35°13° FebMarch: average high 50 °F, low 23 °F 50°23° MarApril: average high 59 °F, low 32 °F 59°32° AprMay: average high 68 °F, low 41 °F 68°41° MayJune: average high 78 °F, low 49 °F 78°49° JunJuly: average high 86 °F, low 55 °F 86°55° JulAugust: average high 84 °F, low 53 °F 84°53° AugSeptember: average high 74 °F, low 44 °F 74°44° SepOctober: average high 58 °F, low 32 °F 58°32° OctNovember: average high 43 °F, low 20 °F 43°20° NovDecember: average high 32 °F, low 10 °F 32°10° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 0.24 in precipitation, 2.8 in snowfall 0.2❄3 JanFebruary: 0.26 in precipitation, 3.1 in snowfall 0.3❄3 FebMarch: 0.36 in precipitation, 1.2 in snowfall 0.4❄1 MarApril: 0.83 in precipitation, 2 in snowfall 0.8❄2 AprMay: 1.41 in precipitation, 0.2 in snowfall 1.4 MayJune: 1.31 in precipitation 1.3 JunJuly: 0.63 in precipitation 0.6 JulAugust: 0.42 in precipitation 0.4 AugSeptember: 1.00 in precipitation 1.0 SepOctober: 0.76 in precipitation, 1.2 in snowfall 0.8❄1 OctNovember: 0.29 in precipitation, 2.5 in snowfall 0.3❄3 NovDecember: 0.22 in precipitation, 3.3 in snowfall 0.2❄3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Emblem, WY (11 mi away); precipitation: Emblem, WY (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

824104b
Basin, WY · 7 mi
824225a
Emblem, WY · 11 mi
824115a
Burlington, WY · 11 mi
824264b
Greybull, WY · 17 mi
824324b
Manderson, WY · 24 mi
824014b
Worland, WY · 24 mi
824125a
Byron, WY · 33 mi
824315a
Lovell, WY · 37 mi

Wyoming planting zones →

Questions about 82434

What planting zone is ZIP code 82434?

ZIP code 82434 (Otto, WY) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Otto, WY?

The median last spring frost (32 °F) near 82434 is May 12; after May 27 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Emblem station.

When is the first frost in Otto, WY?

The median first fall frost near 82434 is September 28, giving a median frost-free growing season of 136 days.

When should I plant tomatoes in 82434?

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 82434 get?

About 7.7 inches of precipitation a year and 16 inches of snowfall (NOAA 1991–2020 normals, Emblem station).

How hot do summers get in Otto, WY?

The average high peaks at 86 °F in July, with about 28 days a year at 90 °F or more.

What kind of soil does 82434 have?

The USDA soil survey maps Bributte at the center of ZIP 82434: clay, well drained, pH about 8.4 (alkaline).

Did spring come early in Otto, WY in 2026?

Spring leaf-out near 82434 came on Mar 21 in 2026, 18 days earlier than the 1991–2020 average (Apr 8), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Otto, WY?

Long-day onions: the longest day near 82434 is 15 h 32 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).