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

Planting zone for 81220 — Cimarron, CO

ZIP code 81220 (Cimarron, Montrose County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is June 20 and the first fall frost September 10.

Where ZIP 81220 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.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostJun 20
First frostSep 10
2012 zone5b

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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Cimarron, CO…

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 Cimarron, CO

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostJune 20median — 50% chance of a later frost
Safe for tender plantsJuly 7only 10% chance of frost after
First fall frostSeptember 10median — 10% chance by Aug 23
Growing season81 daysfrost-free, median

A hard freeze (28 °F) usually ends around June 2 and returns around September 21.

From the NOAA station Cimarron, CO — 11 miles away, elevation 6,890 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 81220

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · May 9 – May 23
SpinachSow outdoors · May 9 – May 30
Broccoli, cabbageStart indoors · Apr 11 – Apr 25
Broccoli, cabbageTransplant · May 30 – Jun 13
Onion setsPlant outdoors · May 23 – Jun 6
PotatoesPlant outdoors · May 30 – Jun 13
LettuceSow outdoors · May 23 – Jun 6
Carrots, beetsSow outdoors · May 30 – Jun 13
TomatoesStart indoors · Apr 25 – May 9
TomatoesTransplant · Jun 27 – Jul 11
Peppers, eggplantStart indoors · Apr 11 – Apr 25
Peppers, eggplantTransplant · Jul 4 – Jul 18
BeansSow outdoors · Jun 27 – Jul 11
Sweet cornSow outdoors · Jun 27 – Jul 11
Cucumbers, squashSow outdoors · Jun 27 – Jul 11
Fall lettuce, spinachSow outdoors · Jul 16 – Jul 30
GarlicPlant cloves · Aug 27 – Oct 1
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 20) and first fall frost (Sep 10) 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 81220 came on Apr 26 — 8 days earlier than the 1991–2020 average (May 4).

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 5b in Colorado

546 plants native to the lower 48 states, recorded in Colorado, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. Each links to its USDA PLANTS profile.

Trees 27

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 °Fblack walnut100 ft · blooms late spring · high shade tolerance · to −28 °Fblack willow100 ft · blooms early spring · high shade tolerance · to −58 °Fblue spruce100 ft · blooms late spring · medium shade tolerance · to −38 °F

Shrubs 98

alderleaf 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 °FApache plume6 ft · blooms late spring · high shade tolerance · to −23 °F

Wildflowers & perennials 246

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine aster0.3 ft · blooms early summer · medium shade tolerance · to −28 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °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 163

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

riverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °FVirginia creeper1 ft · blooms late spring · medium shade tolerance · to −28 °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 Cimarron, CO.

Soil in Cimarron, CO

The soil mapped at the center of ZIP 81220 is Frisco — moderately decomposed plant material, well drained.

TextureModerately decomposed plant materialtop layer
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter70%high
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Frisco gravelly loam, 5 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 81220; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Cimarron, CO

Summer high86 °Faverage high, July
Winter low3 °Faverage low, January
Hot days10days a year at 90 °F or more
Freezing nights235nights a year at 32 °F or less
Growing degree days1,503base 50 °F — the season’s usable heat
Longest day14 h 50 mindaylight on June 21
Shortest day9 h 30 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation14.3 inper year, rain and melted snow
Snowfall67 inper year

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 35 °F, low 3 °F 35°3° JanFebruary: average high 40 °F, low 10 °F 40°10° FebMarch: average high 51 °F, low 19 °F 51°19° MarApril: average high 60 °F, low 26 °F 60°26° AprMay: average high 70 °F, low 32 °F 70°32° MayJune: average high 81 °F, low 38 °F 81°38° JunJuly: average high 86 °F, low 45 °F 86°45° JulAugust: average high 83 °F, low 45 °F 83°45° AugSeptember: average high 76 °F, low 37 °F 76°37° SepOctober: average high 64 °F, low 26 °F 64°26° OctNovember: average high 49 °F, low 16 °F 49°16° NovDecember: average high 36 °F, low 6 °F 36°6° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 1.09 in precipitation, 14.5 in snowfall 1.1❄15 JanFebruary: 0.94 in precipitation, 11.6 in snowfall 0.9❄12 FebMarch: 0.91 in precipitation, 8.2 in snowfall 0.9❄8 MarApril: 1.22 in precipitation, 5.7 in snowfall 1.2❄6 AprMay: 1.28 in precipitation, 1.1 in snowfall 1.3❄1 MayJune: 0.68 in precipitation 0.7 JunJuly: 1.37 in precipitation 1.4 JulAugust: 1.41 in precipitation 1.4 AugSeptember: 1.82 in precipitation 1.8 SepOctober: 1.35 in precipitation, 1.4 in snowfall 1.4❄1 OctNovember: 1.04 in precipitation, 9.7 in snowfall 1.0❄10 NovDecember: 1.17 in precipitation, 14.5 in snowfall 1.2❄15 Dec

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

Nearby ZIP codes

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

812435b
Powderhorn, CO · 16 mi
814326a
Ridgway, CO · 19 mi
814275b
Ouray, CO · 20 mi
814016b
Montrose, CO · 22 mi
812355a
Lake City, CO · 23 mi
814156a
Crawford, CO · 24 mi
814036a
Montrose, CO · 24 mi
814026b
Montrose, CO · 26 mi

Colorado planting zones →

Questions about 81220

What planting zone is ZIP code 81220?

ZIP code 81220 (Cimarron, CO) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Cimarron, CO?

The median last spring frost (32 °F) near 81220 is June 20; after July 7 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Cimarron station.

When is the first frost in Cimarron, CO?

The median first fall frost near 81220 is September 10, giving a median frost-free growing season of 81 days.

When should I plant tomatoes in 81220?

Start tomato seeds indoors around Apr 25 – May 9 and set transplants outside around Jun 27 – Jul 11, one to three weeks after the median last frost.

How much rain and snow does 81220 get?

About 14.3 inches of precipitation a year and 67 inches of snowfall (NOAA 1991–2020 normals, Cimarron station).

How hot do summers get in Cimarron, CO?

The average high peaks at 86 °F in July, with about 10 days a year at 90 °F or more.

What kind of soil does 81220 have?

The USDA soil survey maps Frisco at the center of ZIP 81220: moderately decomposed plant material, well drained, pH about 5.0 (strongly acidic).

Did spring come early in Cimarron, CO in 2026?

Spring leaf-out near 81220 came on Apr 26 in 2026, 8 days earlier than the 1991–2020 average (May 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Cimarron, CO?

Intermediate onions: the longest day near 81220 is 14 h 50 min, so day-neutral types bulb best; long-day varieties may not bulb fully.