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

Planting zone for 80534 — Johnstown, CO

ZIP code 80534 (Johnstown, Weld County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 10 and the first fall frost October 1.

Where ZIP 80534 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.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostMay 10
First frostOct 1
2012 zone5b

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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Johnstown, 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 Johnstown, CO

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 10median — 50% chance of a later frost
Safe for tender plantsMay 22only 10% chance of frost after
First fall frostOctober 1median — 10% chance by Sep 15
Growing season142 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 10.

From the NOAA station Loveland 2n, CO — 11 miles away, elevation 5,079 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 80534

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 29 – Apr 12
SpinachSow outdoors · Mar 29 – Apr 19
Broccoli, cabbageStart indoors · Mar 1 – Mar 15
Broccoli, cabbageTransplant · Apr 19 – May 3
Onion setsPlant outdoors · Apr 12 – Apr 26
PotatoesPlant outdoors · Apr 19 – May 3
LettuceSow outdoors · Apr 12 – Apr 26
Carrots, beetsSow outdoors · Apr 19 – May 3
TomatoesStart indoors · Mar 15 – Mar 29
TomatoesTransplant · May 17 – May 31
Peppers, eggplantStart indoors · Mar 1 – Mar 15
Peppers, eggplantTransplant · May 24 – Jun 7
BeansSow outdoors · May 17 – May 31
Sweet cornSow outdoors · May 17 – May 31
Cucumbers, squashSow outdoors · May 17 – May 31
Fall lettuce, spinachSow outdoors · Aug 6 – Aug 20
GarlicPlant cloves · Sep 17 – Oct 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 10) and first fall frost (Oct 1) 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 80534 came on Feb 25 — 30 days earlier than the 1991–2020 average (Mar 27).

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 5b in Colorado

546 plants native to the lower 48 states, recorded in Colorado, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. 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 98

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 246

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 163

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 Johnstown, CO.

Soil in Johnstown, CO

The soil mapped at the center of ZIP 80534 is Nunn — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH7.2neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classFarmland of statewide importanceUSDA classification

Map unit: Nunn clay loam, 1 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 80534; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Johnstown, CO

Summer high89 °Faverage high, July
Winter low13 °Faverage low, January
Hot days38days a year at 90 °F or more
Freezing nights174nights a year at 32 °F or less
Growing degree days2,510base 50 °F — the season’s usable heat
Longest day15 h 03 mindaylight on June 21
Shortest day9 h 17 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation14.4 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 44 °F, low 13 °F 44°13° JanFebruary: average high 46 °F, low 15 °F 46°15° FebMarch: average high 56 °F, low 23 °F 56°23° MarApril: average high 62 °F, low 31 °F 62°31° AprMay: average high 71 °F, low 40 °F 71°40° MayJune: average high 83 °F, low 49 °F 83°49° JunJuly: average high 89 °F, low 55 °F 89°55° JulAugust: average high 87 °F, low 53 °F 87°53° AugSeptember: average high 79 °F, low 44 °F 79°44° SepOctober: average high 65 °F, low 32 °F 65°32° OctNovember: average high 53 °F, low 21 °F 53°21° NovDecember: average high 44 °F, low 13 °F 44°13° Dec

Precipitation by month inches

0″1″2″3″January: 0.39 in precipitation 0.4 JanFebruary: 0.39 in precipitation 0.4 FebMarch: 0.92 in precipitation 0.9 MarApril: 1.74 in precipitation 1.7 AprMay: 2.63 in precipitation 2.6 MayJune: 1.79 in precipitation 1.8 JunJuly: 1.54 in precipitation 1.5 JulAugust: 1.44 in precipitation 1.4 AugSeptember: 1.36 in precipitation 1.4 SepOctober: 1.08 in precipitation 1.1 OctNovember: 0.65 in precipitation 0.7 NovDecember: 0.51 in precipitation 0.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Loveland 2n, CO (11 mi away); precipitation: Milliken 1.3 Wsw, CO (4 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.

805435b
Milliken, CO · 4 mi
805425b
Mead, CO · 7 mi
805395b
Loveland, CO · 9 mi
806235a
Gilcrest, CO · 9 mi
806345b
Greeley, CO · 9 mi
806515b
Platteville, CO · 9 mi
806325a
Greeley, CO · 10 mi
805135b
Berthoud, CO · 10 mi

Colorado planting zones →

Questions about 80534

What planting zone is ZIP code 80534?

ZIP code 80534 (Johnstown, CO) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Johnstown, CO?

The median last spring frost (32 °F) near 80534 is May 10; after May 22 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Loveland 2n station.

When is the first frost in Johnstown, CO?

The median first fall frost near 80534 is October 1, giving a median frost-free growing season of 142 days.

When should I plant tomatoes in 80534?

Start tomato seeds indoors around Mar 15 – Mar 29 and set transplants outside around May 17 – May 31, one to three weeks after the median last frost.

How much rain and snow does 80534 get?

About 14.4 inches of precipitation a year (NOAA 1991–2020 normals, Milliken 1.3 Wsw station).

How hot do summers get in Johnstown, CO?

The average high peaks at 89 °F in July, with about 38 days a year at 90 °F or more.

What kind of soil does 80534 have?

The USDA soil survey maps Nunn at the center of ZIP 80534: clay loam, well drained, pH about 7.2 (neutral).

Did spring come early in Johnstown, CO in 2026?

Spring leaf-out near 80534 came on Feb 25 in 2026, 30 days earlier than the 1991–2020 average (Mar 27), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Johnstown, CO?

Long-day onions: the longest day near 80534 is 15 h 03 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).