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

Planting zone for 81251 — Twin Lakes, CO

ZIP code 81251 (Twin Lakes, Lake County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is June 16 and the first fall frost September 10.

Where ZIP 81251 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.

Zone5a−20 to −15 °F
Coldest night−28.9 to −26.1 °C
Last frostJun 16
First frostSep 10
2012 zone4b

Was 4b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Twin Lakes, 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 Twin Lakes, CO

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostJune 16median — 50% chance of a later frost
Safe for tender plantsJune 29only 10% chance of frost after
First fall frostSeptember 10median — 10% chance by Aug 24
Growing season85 daysfrost-free, median

A hard freeze (28 °F) usually ends around June 2 and returns around September 23.

From the NOAA station Twin Lakes Rsvr, CO — 6 miles away, elevation 9,236 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 81251

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · May 5 – May 19
SpinachSow outdoors · May 5 – May 26
Broccoli, cabbageStart indoors · Apr 7 – Apr 21
Broccoli, cabbageTransplant · May 26 – Jun 9
Onion setsPlant outdoors · May 19 – Jun 2
PotatoesPlant outdoors · May 26 – Jun 9
LettuceSow outdoors · May 19 – Jun 2
Carrots, beetsSow outdoors · May 26 – Jun 9
TomatoesStart indoors · Apr 21 – May 5
TomatoesTransplant · Jun 23 – Jul 7
Peppers, eggplantStart indoors · Apr 7 – Apr 21
Peppers, eggplantTransplant · Jun 30 – Jul 14
BeansSow outdoors · Jun 23 – Jul 7
Sweet cornSow outdoors · Jun 23 – Jul 7
Cucumbers, squashSow outdoors · Jun 23 – Jul 7
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 16) 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 81251 came on May 28 — 10 days earlier than the 1991–2020 average (Jun 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 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.

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 95

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 239

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 159

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 Twin Lakes, CO.

Soil in Twin Lakes, CO

The soil mapped at the center of ZIP 81251 is Leighcan 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: Leighcan family-Rock outcrop complex, 40 to 70 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 81251; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Twin Lakes, CO

Summer high74 °Faverage high, July
Winter low5 °Faverage low, January
Hot days0days a year at 90 °F or more
Freezing nights240nights a year at 32 °F or less
Growing degree days674base 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
Precipitation10.3 inper year, rain and melted snow

Average high and low, by month

−10°0°10°20°30°40°50°60°70°80°32 °FJanuary: average high 34 °F, low 5 °F 34°5° JanFebruary: average high 35 °F, low 5 °F 35°5° FebMarch: average high 41 °F, low 13 °F 41°13° MarApril: average high 46 °F, low 21 °F 46°21° AprMay: average high 58 °F, low 30 °F 58°30° MayJune: average high 70 °F, low 37 °F 70°37° JunJuly: average high 74 °F, low 43 °F 74°43° JulAugust: average high 71 °F, low 42 °F 71°42° AugSeptember: average high 65 °F, low 35 °F 65°35° SepOctober: average high 53 °F, low 26 °F 53°26° OctNovember: average high 42 °F, low 17 °F 42°17° NovDecember: average high 34 °F, low 8 °F 34°8° Dec

Precipitation by month inches

0″1″2″January: 0.44 in precipitation 0.4 JanFebruary: 0.57 in precipitation 0.6 FebMarch: 0.70 in precipitation 0.7 MarApril: 0.83 in precipitation 0.8 AprMay: 0.92 in precipitation 0.9 MayJune: 0.72 in precipitation 0.7 JunJuly: 1.67 in precipitation 1.7 JulAugust: 1.56 in precipitation 1.6 AugSeptember: 1.13 in precipitation 1.1 SepOctober: 0.82 in precipitation 0.8 OctNovember: 0.46 in precipitation 0.5 NovDecember: 0.49 in precipitation 0.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Twin Lakes Rsvr, CO (6 mi away); precipitation: Twin Lakes Rsvr, CO (6 mi away). 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.

804295a
Climax, CO · 9 mi
804615a
Leadville, CO · 11 mi
812285a
Granite, CO · 12 mi
812115b
Buena Vista, CO · 12 mi
816115a
Aspen, CO · 12 mi
816425a
Meredith, CO · 14 mi
804405b
Fairplay, CO · 21 mi
804205a
Alma, CO · 21 mi

Colorado planting zones →

Questions about 81251

What planting zone is ZIP code 81251?

ZIP code 81251 (Twin Lakes, CO) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Twin Lakes, CO?

The median last spring frost (32 °F) near 81251 is June 16; after June 29 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Twin Lakes Rsvr station.

When is the first frost in Twin Lakes, CO?

The median first fall frost near 81251 is September 10, giving a median frost-free growing season of 85 days.

When should I plant tomatoes in 81251?

Start tomato seeds indoors around Apr 21 – May 5 and set transplants outside around Jun 23 – Jul 7, one to three weeks after the median last frost.

How much rain and snow does 81251 get?

About 10.3 inches of precipitation a year (NOAA 1991–2020 normals, Twin Lakes Rsvr station).

How hot do summers get in Twin Lakes, CO?

The average high peaks at 74 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 81251 have?

The USDA soil survey maps Leighcan family at the center of ZIP 81251: slightly decomposed plant material, somewhat excessively drained, pH about 5.0 (strongly acidic).

Did spring come early in Twin Lakes, CO in 2026?

Spring leaf-out near 81251 came on May 28 in 2026, 10 days earlier than the 1991–2020 average (Jun 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Twin Lakes, CO?

Intermediate onions: the longest day near 81251 is 14 h 55 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 81251 change?

Yes. The 2012 USDA map put 81251 in zone 4b; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.