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

Planting zone for 84520 — East Carbon, UT

ZIP code 84520 (East Carbon, Carbon County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 26 and the first fall frost October 25.

Where ZIP 84520 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.

Zone6b−5 to 0 °F

Coldest night−20.6 to −17.8 °C

Last frostApr 26

First frostOct 25

2012 zone6b

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 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for East Carbon, UT…

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 East Carbon, UT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 26median — 50% chance of a later frost

Safe for tender plantsMay 18only 10% chance of frost after

First fall frostOctober 25median — 10% chance by Oct 7

Growing season181 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 7 and returns around November 7.

From the NOAA station Sunnyside City, UT — 2 miles away, elevation 6,513 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 84520

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 15 – Mar 29

SpinachSow outdoors · Mar 15 – Apr 5

Broccoli, cabbageStart indoors · Feb 15 – Mar 1

Broccoli, cabbageTransplant · Apr 5 – Apr 19

Onion setsPlant outdoors · Mar 29 – Apr 12

PotatoesPlant outdoors · Apr 5 – Apr 19

LettuceSow outdoors · Mar 29 – Apr 12

Carrots, beetsSow outdoors · Apr 5 – Apr 19

TomatoesStart indoors · Mar 1 – Mar 15

TomatoesTransplant · May 3 – May 17

Peppers, eggplantStart indoors · Feb 15 – Mar 1

Peppers, eggplantTransplant · May 10 – May 24

BeansSow outdoors · May 3 – May 17

Sweet cornSow outdoors · May 3 – May 17

Cucumbers, squashSow outdoors · May 3 – May 17

Fall lettuce, spinachSow outdoors · Aug 30 – Sep 13

GarlicPlant cloves · Oct 11 – Nov 15

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 26) and first fall frost (Oct 25) 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 84520 came on Mar 11 — 23 days earlier than the 1991–2020 average (Apr 3).

average
Apr 32026
Mar 11

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 6b in Utah

549 plants native to the lower 48 states, recorded in Utah, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. 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 East Carbon, UT.

Soil in East Carbon, UT

The soil mapped at the center of ZIP 84520 is Strych — very stony loam, well drained.

TextureVery stony loama good balance for most vegetables

pH7.9alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter0.75%low — add compost

Hydrologic groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Strych very stony loam, dry, 3 to 30 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 84520; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in East Carbon, UT

Summer high89 °Faverage high, July

Winter low22 °Faverage low, January

Hot days36days a year at 90 °F or more

Freezing nights128nights a year at 32 °F or less

Growing degree days2,773base 50 °F — the season’s usable heat

Longest day14 h 58 mindaylight on June 21

Shortest day9 h 22 mindaylight on December 21

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

Precipitation15.3 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: Sunnyside City, UT (2 mi away); precipitation: Sunnyside City, UT (2 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.

845396b

Sunnyside, UT · 3 mi

845426a

Wellington, UT · 15 mi

Kenilworth, UT · 23 mi

845186a

Cleveland, UT · 26 mi

845266a

Helper, UT · 31 mi

845256b

Green River, UT · 33 mi

Utah planting zones →

Questions about 84520

What planting zone is ZIP code 84520?

ZIP code 84520 (East Carbon, UT) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in East Carbon, UT?

The median last spring frost (32 °F) near 84520 is April 26; after May 18 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Sunnyside City station.

When is the first frost in East Carbon, UT?

The median first fall frost near 84520 is October 25, giving a median frost-free growing season of 181 days.

When should I plant tomatoes in 84520?

Start tomato seeds indoors around Mar 1 – Mar 15 and set transplants outside around May 3 – May 17, one to three weeks after the median last frost.

How much rain and snow does 84520 get?

About 15.3 inches of precipitation a year (NOAA 1991–2020 normals, Sunnyside City station).

How hot do summers get in East Carbon, UT?

The average high peaks at 89 °F in July, with about 36 days a year at 90 °F or more.

What kind of soil does 84520 have?

The USDA soil survey maps Strych at the center of ZIP 84520: very stony loam, well drained, pH about 7.9 (alkaline).

Did spring come early in East Carbon, UT in 2026?

Spring leaf-out near 84520 came on Mar 11 in 2026, 23 days earlier than the 1991–2020 average (Apr 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in East Carbon, UT?

Intermediate onions: the longest day near 84520 is 14 h 58 min, so day-neutral types bulb best; long-day varieties may not bulb fully.