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

Planting zone for Aspen, CO

Aspen, CO is in USDA zone 5a across its 2 ZIP codes. The median last spring frost is June 2 and the first fall frost September 23.

Aspen on the zone map

Outlined: its 2 ZIP code areas · 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

ZIP codes2

Last frostJun 2

First frostSep 23

Growing season113 days

5a 2 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

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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 Aspen, CO

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 2median — 50% chance of a later frost

Safe for tender plantsJune 17only 10% chance of frost after

First fall frostSeptember 23median — 10% chance by Sep 12

Growing season113 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 18 and returns around October 1.

From the NOAA station Aspen 1sw, CO, elevation 8,176 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 Aspen

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 21 – May 5

SpinachSow outdoors · Apr 21 – May 12

Broccoli, cabbageStart indoors · Mar 24 – Apr 7

Broccoli, cabbageTransplant · May 12 – May 26

Onion setsPlant outdoors · May 5 – May 19

PotatoesPlant outdoors · May 12 – May 26

LettuceSow outdoors · May 5 – May 19

Carrots, beetsSow outdoors · May 12 – May 26

TomatoesStart indoors · Apr 7 – Apr 21

TomatoesTransplant · Jun 9 – Jun 23

Peppers, eggplantStart indoors · Mar 24 – Apr 7

Peppers, eggplantTransplant · Jun 16 – Jun 30

BeansSow outdoors · Jun 9 – Jun 23

Sweet cornSow outdoors · Jun 9 – Jun 23

Cucumbers, squashSow outdoors · Jun 9 – Jun 23

Fall lettuce, spinachSow outdoors · Jul 29 – Aug 12

GarlicPlant cloves · Sep 9 – Oct 14

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 2) and first fall frost (Sep 23) 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 81611 came on May 15 — 11 days earlier than the 1991–2020 average (May 26).

average
May 262026
May 15

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 Colorado

532 plants native to the lower 48 states, recorded in Colorado, 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 Aspen, CO.

Soil in Aspen, CO

The soil mapped at the center of ZIP 81611 is Moran family — slightly decomposed plant material, somewhat excessively drained.

TextureSlightly decomposed plant materialtop layer

pH5.0strongly acidic; most vegetables like 6.0–7.0

DrainageSomewhat excessively drainednatural drainage class

Organic matter75%high

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Moran family-Rock outcrop-Cryaquolls complex, 0 to 40 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 81611; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Aspen, CO

Summer high76 °Faverage high, July

Winter low10 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights210nights a year at 32 °F or less

Growing degree days1,109base 50 °F — the season’s usable heat

Longest day14 h 55 mindaylight on June 21

Shortest day9 h 25 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation30.3 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: Aspen 1sw, CO (9 mi away); precipitation: Independence Pass, CO (6 mi away). Daylight is calculated from latitude.

ZIP codes in Aspen

Colorado planting zones →

Questions about Aspen

What planting zone is Aspen, CO?

Aspen, CO is in USDA hardiness zone 5a on the 2023 map (5a: −20 to −15 °F).

When is the last frost in Aspen, CO?

The median last spring frost is June 2 and the median first fall frost is September 23 (NOAA 1991–2020 normals, Aspen 1sw station).

When can I plant a garden in Aspen, CO?

Cool-season crops like peas and spinach go in around Apr 21 – May 12; tomatoes, peppers, beans and squash after about Jun 9, once frost risk has passed.

What kind of onions grow in Aspen, CO?

Intermediate onions: the longest day is 14 h 55 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

How much rain and snow does Aspen, CO get?

About 30.3 inches of precipitation a year (NOAA 1991–2020 normals).