What does USDA hardiness zone 5b mean in Wyoming?

Zone 5b means an average annual extreme minimum winter temperature of −15 to −10 °F — the standard USDA measure of which perennials survive winter. 12 locations in Wyoming fall in this zone. It does not set planting dates; see the frost calendar below for that.

Where in Wyoming's zone 5b is the growing season longest?

Albin runs the longest season on this page at about 142 days; Nordic is shortest at about 71 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.

When should I plant tomatoes in Wyoming's zone 5b?

Using Arrowhead Springs's frost dates (this page's median-season location): start seeds indoors about Mar 27 – Apr 10, then transplant outside about May 29 – Jun 5. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.

Does every location in Wyoming's zone 5b have the same frost dates?

No — they do not all share a weather station, so frost dates vary by a week or more across the 12 locations listed (see the table above for each location's own dates).

USDA zone 5b in Wyoming

−15 to −10 °F avg. annual extreme minimum · 12 locations in this group · NOAA 1991–2020 normals

USDA plant hardiness zone 5b covers 12 locations across Wyoming (average annual extreme minimum −15 to −10 °F): Albin, WY, Arrowhead Springs, WY, Bairoil, WY, Carpenter, WY, Chugwater, WY, Dixon, WY, and 6 more. Average last spring frost across this group ranges May 12 (Ranchettes) to June 20 (Nordic), and growing seasons run 71–142 days (Nordic to Albin) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Wyoming location's own frost dates; the printable planting calendar uses Arrowhead Springs, this group's median-season location.

USDA zone: 5b−15 to −10 °F
Last frost range: May 12–Jun 20avg, 32°F
First frost range: Sep 1–Oct 2avg, 32°F
Growing season range: 71–142days

Locations in this group

Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.

Own frost dates per location.
Location	Also covers	Nearest station	Last frost	First frost	Season (days)
Albin	—	Albin	May 14	Oct 2	142
Arrowhead Springs *	—	Rock Springs Ap	May 22	Sep 28	126
Bairoil	—	Muddy Gap	May 21	Sep 27	126
Carpenter	—	Carpenter 3n	May 14	Sep 26	133
Chugwater	—	Sybille Rsch Unit	May 22	Sep 24	125
Dixon	—	Baggs	Jun 1	Sep 18	108
Laramie	—	Hecla 1e	May 27	Sep 19	115
Lonetree	Fort Bridger, Mountain View	Mtn View	Jun 14	Sep 9	84
McKinnon	Manila	Manila	May 22	Sep 29	128
Nordic	Turnerville, Afton, Star Valley Ranch, Thayne	Afton	Jun 20	Sep 1	71
Ranchettes	Warren AFB, Fox Farm-College	Cheyenne	May 12	Oct 1	141
Wilson	—	Alta 1 Nnw	Jun 14	Sep 11	85

* Arrowhead Springs is this group's median-season location — the calendar below is computed from its data.

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.

Planting calendar (Arrowhead Springs, representative)

Computed from Arrowhead Springs's average frost dates — the median-season location in this Wyomingzone 5b group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).

Crop

JanFebMarAprMayJunJulAugSepOctNovDec

Tomato

Pepper

Cucumber

Summer squash / zucchini

Start indoors
Plant out
Fall sowing
First harvest

Planting windows for Arrowhead Springs (Wyoming, zone 5b), this group's representative location.
Crop	Frost tolerance	Start indoors	Plant out	First harvest	Fall planting	Season fit
Tomato	Tender	Mar 27 – Apr 10	May 29 – Jun 5	Jul 28 – Aug 17	—	matures comfortably
Pepper	Very tender	Mar 13 – Mar 27	Jun 5 – Jun 12	Aug 4 – Sep 3	—	matures comfortably
Cucumber	Tender	Apr 24 – May 1	May 29 – Jun 5	Jul 18 – Aug 7	—	matures comfortably
Summer squash / zucchini	Tender	—	May 29 – Jun 5	Jul 13 – Jul 28	—	matures comfortably
Bush bean	Tender	—	May 29 – Jun 5	Jul 18 – Jul 28	Jul 30 – Aug 9	matures comfortably
Sweet corn	Tender	—	May 22 – Jun 5	Jul 21 – Aug 20	—	matures comfortably
Basil	Very tender	Apr 10 – Apr 24	May 29 – Jun 5	Jun 28 – Jul 13	—	matures comfortably
Lettuce	Half-hardy	Apr 10 – Apr 24	Apr 24 – May 8	Jun 8 – Jun 23	Jul 16 – Jul 31	matures comfortably
Pea	Hardy	—	Apr 10 – Apr 24	Jun 4 – Jun 19	Jul 6 – Jul 21	matures comfortably
Spinach	Hardy	—	Apr 10 – Apr 24	May 20 – May 30	Jul 26 – Aug 5	matures comfortably
Carrot	Half-hardy	—	May 1 – May 8	Jun 30 – Jul 20	Jun 26 – Jul 16	matures comfortably
Broccoli	Half-hardy	Mar 27 – Apr 10	Apr 24 – May 8	Jun 18 – Jul 8	Jul 1 – Jul 21	matures comfortably

Which crops fit this growing season

Using Arrowhead Springs's own 126-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.

Frost & freeze dates (Arrowhead Springs)

From NOAA's 1991–2020 Climate Normals at station USW00024027. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.

Freeze probabilities by temperature threshold (MM/DD, NOAA 1991–2020), Arrowhead Springs.
Threshold	Last spring — avg	Last spring — 90%-safe	First fall — avg	First fall — 90%-safe	Season (days)
36°F	Jun 5	Jun 21	Sep 19	Sep 30	104
32°F (freeze)	May 22	Jun 9	Sep 28	Oct 9	126
28°F	May 7	May 25	Oct 5	Oct 23	149
24°F	Apr 26	May 10	Oct 17	Nov 1	171

Growing degree days

Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 12 locations is 1,874; Arrowhead Springs's own reading is shown below.

Annual growing degree days for Arrowhead Springs (°F·days, NOAA 1991–2020).
Model	°F·days	Used for
Base 50°F (warm-season)	1,914	standard warm-season base (tomato, corn, beans)
Base 40°F (cool-season)	3,656	cool-season crops (brassicas, greens)

Hardiness zone 5b in Wyoming

Zone 5b means an average annual extreme minimum winter temperature of about −15 to −10 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Wyoming spans 4 hardiness zones in this dataset — see all Wyoming locations for the full range, including zones4a, 4b, 5a.

Explore zone 5b in other states at zone 5b, or see all USDA hardiness zones.

Frequently asked questions

What does USDA hardiness zone 5b mean in Wyoming?: Zone 5b means an average annual extreme minimum winter temperature of −15 to −10 °F — the standard USDA measure of which perennials survive winter. 12 locations in Wyoming fall in this zone. It does not set planting dates; see the frost calendar below for that.
Where in Wyoming's zone 5b is the growing season longest?: Albin runs the longest season on this page at about 142 days; Nordic is shortest at about 71 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
When should I plant tomatoes in Wyoming's zone 5b?: Using Arrowhead Springs's frost dates (this page's median-season location): start seeds indoors about Mar 27 – Apr 10, then transplant outside about May 29 – Jun 5. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
Does every location in Wyoming's zone 5b have the same frost dates?: No — they do not all share a weather station, so frost dates vary by a week or more across the 12 locations listed (see the table above for each location's own dates).

Sources & method

Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.