Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 82646 — Natrona, WY

ZIP code 82646 (Natrona, Natrona County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 23 and the first fall frost September 20.

Where ZIP 82646 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 23

First frostSep 20

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 Natrona, 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 Natrona, WY

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 23median — 50% chance of a later frost

Safe for tender plantsJune 5only 10% chance of frost after

First fall frostSeptember 20median — 10% chance by Sep 7

Growing season121 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 10 and returns around October 1.

From the NOAA station Powder River #2, WY — 12 miles away, elevation 5,699 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 82646

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 11 – Apr 25

SpinachSow outdoors · Apr 11 – May 2

Broccoli, cabbageStart indoors · Mar 14 – Mar 28

Broccoli, cabbageTransplant · May 2 – May 16

Onion setsPlant outdoors · Apr 25 – May 9

PotatoesPlant outdoors · May 2 – May 16

LettuceSow outdoors · Apr 25 – May 9

Carrots, beetsSow outdoors · May 2 – May 16

TomatoesStart indoors · Mar 28 – Apr 11

TomatoesTransplant · May 30 – Jun 13

Peppers, eggplantStart indoors · Mar 14 – Mar 28

Peppers, eggplantTransplant · Jun 6 – Jun 20

BeansSow outdoors · May 30 – Jun 13

Sweet cornSow outdoors · May 30 – Jun 13

Cucumbers, squashSow outdoors · May 30 – Jun 13

Fall lettuce, spinachSow outdoors · Jul 26 – Aug 9

GarlicPlant cloves · Sep 6 – Oct 11

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 23) and first fall frost (Sep 20) 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 82646 came on Mar 20 — 25 days earlier than the 1991–2020 average (Apr 14).

average
Apr 142026
Mar 20

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.

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 Natrona, WY.

Soil in Natrona, WY

The soil mapped at the center of ZIP 82646 is Orella — silty clay loam, well drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up

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: Orella-Rock outcrop complex, 3 to 30 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 82646; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Natrona, WY

Summer high88 °Faverage high, July

Winter low10 °Faverage low, January

Hot days33days a year at 90 °F or more

Freezing nights194nights a year at 32 °F or less

Growing degree days2,082base 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)

Precipitation13 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Powder River #2, WY (12 mi away); precipitation: Powder Rvr (School), WY (12 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5a.

826045a

Casper, WY · 5 mi

826485a

Powder River, WY · 11 mi

Wyoming planting zones →

Questions about 82646

What planting zone is ZIP code 82646?

ZIP code 82646 (Natrona, 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 Natrona, WY?

The median last spring frost (32 °F) near 82646 is May 23; after June 5 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Powder River #2 station.

When is the first frost in Natrona, WY?

The median first fall frost near 82646 is September 20, giving a median frost-free growing season of 121 days.

When should I plant tomatoes in 82646?

Start tomato seeds indoors around Mar 28 – Apr 11 and set transplants outside around May 30 – Jun 13, one to three weeks after the median last frost.

How much rain and snow does 82646 get?

About 13 inches of precipitation a year (NOAA 1991–2020 normals, Powder Rvr (School) station).

How hot do summers get in Natrona, WY?

The average high peaks at 88 °F in July, with about 33 days a year at 90 °F or more.

What kind of soil does 82646 have?

The USDA soil survey maps Orella at the center of ZIP 82646: silty clay loam, well drained, pH about 8.5 (alkaline).

Did spring come early in Natrona, WY in 2026?

Spring leaf-out near 82646 came on Mar 20 in 2026, 25 days earlier than the 1991–2020 average (Apr 14), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Natrona, WY?

Long-day onions: the longest day near 82646 is 15 h 22 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 82646 change?

Yes. The 2012 USDA map put 82646 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.