Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 30, 2026

Planting zone for Silverthorne, CO

Silverthorne, CO is in USDA zones 4b to 5a across its 2 ZIP codes. The median last spring frost is June 21 and the first fall frost September 7.

Silverthorne on the zone map

Outlined: its 1 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.

Zones4b–5a−25 to −15 °F

ZIP codes2

Last frostJun 21

First frostSep 7

Growing season77 days

4b 1 ZIP 5a 1 ZIP

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Silverthorne, 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 Silverthorne, CO

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 21median — 50% chance of a later frost

Safe for tender plantsJuly 9only 10% chance of frost after

First fall frostSeptember 7median — 10% chance by Aug 26

Growing season77 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 31 and returns around September 21.

From the NOAA station Vail, CO, elevation 8,304 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 Silverthorne

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · May 10 – May 24

SpinachSow outdoors · May 10 – May 31

Broccoli, cabbageStart indoors · Apr 12 – Apr 26

Broccoli, cabbageTransplant · May 31 – Jun 14

Onion setsPlant outdoors · May 24 – Jun 7

PotatoesPlant outdoors · May 31 – Jun 14

LettuceSow outdoors · May 24 – Jun 7

Carrots, beetsSow outdoors · May 31 – Jun 14

TomatoesStart indoors · Apr 26 – May 10

TomatoesTransplant · Jun 28 – Jul 12

Peppers, eggplantStart indoors · Apr 12 – Apr 26

Peppers, eggplantTransplant · Jul 5 – Jul 19

BeansSow outdoors · Jun 28 – Jul 12

Sweet cornSow outdoors · Jun 28 – Jul 12

Cucumbers, squashSow outdoors · Jun 28 – Jul 12

Fall lettuce, spinachSow outdoors · Jul 13 – Jul 27

GarlicPlant cloves · Aug 24 – Sep 28

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 21) and first fall frost (Sep 7) 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 80498 came on May 14 — 8 days earlier than the 1991–2020 average (May 22).

average
May 222026
May 14

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 4b in Colorado

484 plants native to the lower 48 states, recorded in Colorado, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. 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 Silverthorne, CO.

Soil in Silverthorne, CO

The soil mapped at the center of ZIP 80498 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-Teewinot family, extremely stony complex, 40 to 75 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 80498; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Silverthorne, CO

Summer high77 °Faverage high, July

Winter low7 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights248nights a year at 32 °F or less

Growing degree days744base 50 °F — the season’s usable heat

Longest day14 h 59 mindaylight on June 21

Shortest day9 h 21 mindaylight on December 21

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

Precipitation24 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: Vail, CO (9 mi away); precipitation: Summit Ranch, CO (6 mi away). Daylight is calculated from latitude.

ZIP codes in Silverthorne

Colorado planting zones →

Questions about Silverthorne

What planting zone is Silverthorne, CO?

Silverthorne, CO is in USDA hardiness zones 4b to 5a on the 2023 map (4b: −25 to −20 °F; 5a: −20 to −15 °F).

When is the last frost in Silverthorne, CO?

The median last spring frost is June 21 and the median first fall frost is September 7 (NOAA 1991–2020 normals, Vail station).

When can I plant a garden in Silverthorne, CO?

Cool-season crops like peas and spinach go in around May 10 – May 31; tomatoes, peppers, beans and squash after about Jun 28, once frost risk has passed.

What kind of onions grow in Silverthorne, CO?

Intermediate onions: the longest day is 14 h 59 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

How much rain and snow does Silverthorne, CO get?

About 24 inches of precipitation a year (NOAA 1991–2020 normals).