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

Planting zone for 80446 — Granby, CO

ZIP code 80446 (Granby, Grand County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is June 13 and the first fall frost September 7.

Where ZIP 80446 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 13

First frostSep 7

2012 zone4a

Was 4a on the 2012 map — a full 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 Granby, 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 Granby, CO

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 13median — 50% chance of a later frost

Safe for tender plantsJune 28only 10% chance of frost after

First fall frostSeptember 7median — 10% chance by Aug 21

Growing season84 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 26 and returns around September 22.

From the NOAA station Grand Lake 6 Ssw, CO — 4 miles away, elevation 8,288 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 80446

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · May 2 – May 16

SpinachSow outdoors · May 2 – May 23

Broccoli, cabbageStart indoors · Apr 4 – Apr 18

Broccoli, cabbageTransplant · May 23 – Jun 6

Onion setsPlant outdoors · May 16 – May 30

PotatoesPlant outdoors · May 23 – Jun 6

LettuceSow outdoors · May 16 – May 30

Carrots, beetsSow outdoors · May 23 – Jun 6

TomatoesStart indoors · Apr 18 – May 2

TomatoesTransplant · Jun 20 – Jul 4

Peppers, eggplantStart indoors · Apr 4 – Apr 18

Peppers, eggplantTransplant · Jun 27 – Jul 11

BeansSow outdoors · Jun 20 – Jul 4

Sweet cornSow outdoors · Jun 20 – Jul 4

Cucumbers, squashSow outdoors · Jun 20 – Jul 4

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 13) 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 80446 came on Apr 12 — 22 days earlier than the 1991–2020 average (May 4).

average
May 42026
Apr 12

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 Granby, CO.

Soil in Granby, CO

The soil mapped at the center of ZIP 80446 is Binco — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up

pH8.2alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter0.75%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Binco clay loam, 15 to 35 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 80446; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Granby, CO

Summer high75 °Faverage high, July

Winter low3 °Faverage low, January

Hot days0days a year at 90 °F or more

Freezing nights245nights a year at 32 °F or less

Growing degree days778base 50 °F — the season’s usable heat

Longest day15 h 02 mindaylight on June 21

Shortest day9 h 18 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation13.8 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: Grand Lake 6 Ssw, CO (4 mi away); precipitation: Grand Lake 6 Ssw, CO (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

804515b

Hot Sulphur Springs, CO · 10 mi

804785b

Tabernash, CO · 11 mi

804475a

Grand Lake, CO · 11 mi

804425b

Fraser, CO · 17 mi

805105b

Allenspark, CO · 18 mi

Winter Park, CO · 20 mi

Colorado planting zones →

Questions about 80446

What planting zone is ZIP code 80446?

ZIP code 80446 (Granby, 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 Granby, CO?

The median last spring frost (32 °F) near 80446 is June 13; after June 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Grand Lake 6 Ssw station.

When is the first frost in Granby, CO?

The median first fall frost near 80446 is September 7, giving a median frost-free growing season of 84 days.

When should I plant tomatoes in 80446?

Start tomato seeds indoors around Apr 18 – May 2 and set transplants outside around Jun 20 – Jul 4, one to three weeks after the median last frost.

How much rain and snow does 80446 get?

About 13.8 inches of precipitation a year (NOAA 1991–2020 normals, Grand Lake 6 Ssw station).

How hot do summers get in Granby, CO?

The average high peaks at 75 °F in July, with about 0 days a year at 90 °F or more.

What kind of soil does 80446 have?

The USDA soil survey maps Binco at the center of ZIP 80446: clay loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Granby, CO in 2026?

Spring leaf-out near 80446 came on Apr 12 in 2026, 22 days earlier than the 1991–2020 average (May 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Granby, CO?

Long-day onions: the longest day near 80446 is 15 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 80446 change?

Yes. The 2012 USDA map put 80446 in zone 4a; the 2023 map puts it in zone 5a. The newer map uses 1991–2020 data and more weather stations.