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

Planting zone for 81602 — Glenwood Springs, CO

ZIP code 81602 (Glenwood Springs, Garfield County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 13 and the first fall frost October 3.

Where ZIP 81602 is

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.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostMay 13
First frostOct 3
2012 zone6a

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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Glenwood Springs, 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 Glenwood Springs, CO

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 13median — 50% chance of a later frost
Safe for tender plantsMay 30only 10% chance of frost after
First fall frostOctober 3median — 10% chance by Sep 20
Growing season142 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 27 and returns around October 14.

From the NOAA station Glenwood Spgs #2, CO — 2 miles away, elevation 5,896 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 81602

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 1 – Apr 15
SpinachSow outdoors · Apr 1 – Apr 22
Broccoli, cabbageStart indoors · Mar 4 – Mar 18
Broccoli, cabbageTransplant · Apr 22 – May 6
Onion setsPlant outdoors · Apr 15 – Apr 29
PotatoesPlant outdoors · Apr 22 – May 6
LettuceSow outdoors · Apr 15 – Apr 29
Carrots, beetsSow outdoors · Apr 22 – May 6
TomatoesStart indoors · Mar 18 – Apr 1
TomatoesTransplant · May 20 – Jun 3
Peppers, eggplantStart indoors · Mar 4 – Mar 18
Peppers, eggplantTransplant · May 27 – Jun 10
BeansSow outdoors · May 20 – Jun 3
Sweet cornSow outdoors · May 20 – Jun 3
Cucumbers, squashSow outdoors · May 20 – Jun 3
Fall lettuce, spinachSow outdoors · Aug 8 – Aug 22
GarlicPlant cloves · Sep 19 – Oct 24
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 13) and first fall frost (Oct 3) 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 81602 came on Mar 18 — 20 days earlier than the 1991–2020 average (Apr 7).

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 6a in Colorado

563 plants native to the lower 48 states, recorded in Colorado, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

Trees 28

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 104

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 251

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 167

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 4

riverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °Ftrumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °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 Glenwood Springs, CO.

Soil in Glenwood Springs, CO

The soil mapped at the center of ZIP 81602 is Atencio — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH7.6slightly alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter3%moderate
Hydrologic groupBwater soaks in moderately
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Atencio-Azeltine complex, 1 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 81602; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Glenwood Springs, CO

Summer high89 °Faverage high, July
Winter low12 °Faverage low, January
Hot days39days a year at 90 °F or more
Freezing nights174nights a year at 32 °F or less
Growing degree days2,323base 50 °F — the season’s usable heat
Longest day14 h 58 mindaylight on June 21
Shortest day9 h 22 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation19.5 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 36 °F, low 12 °F 36°12° JanFebruary: average high 42 °F, low 19 °F 42°19° FebMarch: average high 53 °F, low 26 °F 53°26° MarApril: average high 60 °F, low 32 °F 60°32° AprMay: average high 71 °F, low 40 °F 71°40° MayJune: average high 82 °F, low 46 °F 82°46° JunJuly: average high 89 °F, low 53 °F 89°53° JulAugust: average high 86 °F, low 52 °F 86°52° AugSeptember: average high 78 °F, low 44 °F 78°44° SepOctober: average high 65 °F, low 33 °F 65°33° OctNovember: average high 49 °F, low 24 °F 49°24° NovDecember: average high 36 °F, low 15 °F 36°15° Dec

Precipitation by month inches

0″1″2″3″January: 1.62 in precipitation 1.6 JanFebruary: 1.65 in precipitation 1.6 FebMarch: 1.50 in precipitation 1.5 MarApril: 2.03 in precipitation 2.0 AprMay: 2.15 in precipitation 2.1 MayJune: 0.96 in precipitation 1.0 JunJuly: 1.29 in precipitation 1.3 JulAugust: 1.45 in precipitation 1.4 AugSeptember: 1.80 in precipitation 1.8 SepOctober: 2.08 in precipitation 2.1 OctNovember: 1.55 in precipitation 1.6 NovDecember: 1.43 in precipitation 1.4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Glenwood Spgs #2, CO (2 mi away); precipitation: Glenwood Springs .64 S, CO (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

816016a
Glenwood Springs, CO · 3 mi
816476a
New Castle, CO · 11 mi
816526a
Silt, CO · 19 mi
816375b
Gypsum, CO · 20 mi
816236a
Carbondale, CO · 23 mi
816216a
Basalt, CO · 27 mi
816546a
Snowmass, CO · 28 mi
804265b
Burns, CO · 29 mi

All 2 ZIP codes in Glenwood Springs → · Colorado planting zones →

Questions about 81602

What planting zone is ZIP code 81602?

ZIP code 81602 (Glenwood Springs, CO) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Glenwood Springs, CO?

The median last spring frost (32 °F) near 81602 is May 13; after May 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Glenwood Spgs #2 station.

When is the first frost in Glenwood Springs, CO?

The median first fall frost near 81602 is October 3, giving a median frost-free growing season of 142 days.

When should I plant tomatoes in 81602?

Start tomato seeds indoors around Mar 18 – Apr 1 and set transplants outside around May 20 – Jun 3, one to three weeks after the median last frost.

How much rain and snow does 81602 get?

About 19.5 inches of precipitation a year (NOAA 1991–2020 normals, Glenwood Springs .64 S station).

How hot do summers get in Glenwood Springs, CO?

The average high peaks at 89 °F in July, with about 39 days a year at 90 °F or more.

What kind of soil does 81602 have?

The USDA soil survey maps Atencio at the center of ZIP 81602: sandy loam, well drained, pH about 7.6 (slightly alkaline).

Did spring come early in Glenwood Springs, CO in 2026?

Spring leaf-out near 81602 came on Mar 18 in 2026, 20 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Glenwood Springs, CO?

Intermediate onions: the longest day near 81602 is 14 h 58 min, so day-neutral types bulb best; long-day varieties may not bulb fully.