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

Planting zone for 81123 — Blanca, CO

ZIP code 81123 (Blanca, Costilla County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 25 and the first fall frost September 22.

Where ZIP 81123 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 frostMay 25

First frostSep 22

2012 zone5a

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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Blanca, 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 Blanca, CO

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 25median — 50% chance of a later frost

Safe for tender plantsJune 12only 10% chance of frost after

First fall frostSeptember 22median — 10% chance by Sep 10

Growing season117 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 13 and returns around October 1.

From the NOAA station Blanca 4 Nw, CO — 5 miles away, elevation 7,710 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 81123

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 13 – Apr 27

SpinachSow outdoors · Apr 13 – May 4

Broccoli, cabbageStart indoors · Mar 16 – Mar 30

Broccoli, cabbageTransplant · May 4 – May 18

Onion setsPlant outdoors · Apr 27 – May 11

PotatoesPlant outdoors · May 4 – May 18

LettuceSow outdoors · Apr 27 – May 11

Carrots, beetsSow outdoors · May 4 – May 18

TomatoesStart indoors · Mar 30 – Apr 13

TomatoesTransplant · Jun 1 – Jun 15

Peppers, eggplantStart indoors · Mar 16 – Mar 30

Peppers, eggplantTransplant · Jun 8 – Jun 22

BeansSow outdoors · Jun 1 – Jun 15

Sweet cornSow outdoors · Jun 1 – Jun 15

Cucumbers, squashSow outdoors · Jun 1 – Jun 15

Fall lettuce, spinachSow outdoors · Jul 28 – Aug 11

GarlicPlant cloves · Sep 8 – Oct 13

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 25) and first fall frost (Sep 22) 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 81123 came on Mar 23 — 22 days earlier than the 1991–2020 average (Apr 14).

average
Apr 142026
Mar 23

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 Blanca, CO.

Soil in Blanca, CO

The soil mapped at the center of ZIP 81123 is Cososa — loamy sand, well drained.

TextureLoamy sanddrains and warms fast; dries out and needs more feeding

pH7.7slightly alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter0.5%low — add compost

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Cososa loamy sand, 0 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 81123; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Blanca, CO

Summer high83 °Faverage high, July

Winter low4 °Faverage low, January

Hot days5days a year at 90 °F or more

Freezing nights215nights a year at 32 °F or less

Growing degree days1,625base 50 °F — the season’s usable heat

Longest day14 h 45 mindaylight on June 21

Shortest day9 h 35 mindaylight on December 21

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

Precipitation10.4 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: Blanca 4 Nw, CO (5 mi away); precipitation: Blanca 0.3 S, CO (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

811335b

Fort Garland, CO · 13 mi

Colorado planting zones →

Questions about 81123

What planting zone is ZIP code 81123?

ZIP code 81123 (Blanca, 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 Blanca, CO?

The median last spring frost (32 °F) near 81123 is May 25; after June 12 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Blanca 4 Nw station.

When is the first frost in Blanca, CO?

The median first fall frost near 81123 is September 22, giving a median frost-free growing season of 117 days.

When should I plant tomatoes in 81123?

Start tomato seeds indoors around Mar 30 – Apr 13 and set transplants outside around Jun 1 – Jun 15, one to three weeks after the median last frost.

How much rain and snow does 81123 get?

About 10.4 inches of precipitation a year (NOAA 1991–2020 normals, Blanca 0.3 S station).

How hot do summers get in Blanca, CO?

The average high peaks at 83 °F in July, with about 5 days a year at 90 °F or more.

What kind of soil does 81123 have?

The USDA soil survey maps Cososa at the center of ZIP 81123: loamy sand, well drained, pH about 7.7 (slightly alkaline).

Did spring come early in Blanca, CO in 2026?

Spring leaf-out near 81123 came on Mar 23 in 2026, 22 days earlier than the 1991–2020 average (Apr 14), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Blanca, CO?

Intermediate onions: the longest day near 81123 is 14 h 45 min, so day-neutral types bulb best; long-day varieties may not bulb fully.