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

Planting zone for 84540 — Thompson, UT

ZIP code 84540 (Thompson, Grand County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is April 27 and the first fall frost October 9.

Where ZIP 84540 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 27

First frostOct 9

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 Thompson, 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 Thompson, UT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostApril 27median — 50% chance of a later frost

Safe for tender plantsMay 9only 10% chance of frost after

First fall frostOctober 9median — 10% chance by Sep 28

Growing season165 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 14 and returns around October 18.

From the NOAA station Dewey, UT — 30 miles away, elevation 4,121 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 84540

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 16 – Mar 30

SpinachSow outdoors · Mar 16 – Apr 6

Broccoli, cabbageStart indoors · Feb 16 – Mar 2

Broccoli, cabbageTransplant · Apr 6 – Apr 20

Onion setsPlant outdoors · Mar 30 – Apr 13

PotatoesPlant outdoors · Apr 6 – Apr 20

LettuceSow outdoors · Mar 30 – Apr 13

Carrots, beetsSow outdoors · Apr 6 – Apr 20

TomatoesStart indoors · Mar 2 – Mar 16

TomatoesTransplant · May 4 – May 18

Peppers, eggplantStart indoors · Feb 16 – Mar 2

Peppers, eggplantTransplant · May 11 – May 25

BeansSow outdoors · May 4 – May 18

Sweet cornSow outdoors · May 4 – May 18

Cucumbers, squashSow outdoors · May 4 – May 18

Fall lettuce, spinachSow outdoors · Aug 14 – Aug 28

GarlicPlant cloves · Sep 25 – Oct 30

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 27) and first fall frost (Oct 9) 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 84540 came on Mar 17 — 18 days earlier than the 1991–2020 average (Apr 4).

average
Apr 42026
Mar 17

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 Thompson, UT.

Soil in Thompson, UT

The soil mapped at the center of ZIP 84540 is Shalako — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding

pH8.2alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Shalako sandy loam, 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 84540; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Thompson, UT

Summer high101 °Faverage high, July

Winter low16 °Faverage low, January

Hot days104days a year at 90 °F or more

Freezing nights154nights a year at 32 °F or less

Growing degree days3,938base 50 °F — the season’s usable heat

Longest day14 h 56 mindaylight on June 21

Shortest day9 h 24 mindaylight on December 21

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

Precipitation20.9 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: Dewey, UT (30 mi away); precipitation: East Willow Creek, UT (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Green River, UT · 39 mi

815236b

Glade Park, CO · 39 mi

East Carbon, UT · 53 mi

Utah planting zones →

Questions about 84540

What planting zone is ZIP code 84540?

ZIP code 84540 (Thompson, 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 Thompson, UT?

The median last spring frost (32 °F) near 84540 is April 27; after May 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Dewey station.

When is the first frost in Thompson, UT?

The median first fall frost near 84540 is October 9, giving a median frost-free growing season of 165 days.

When should I plant tomatoes in 84540?

Start tomato seeds indoors around Mar 2 – Mar 16 and set transplants outside around May 4 – May 18, one to three weeks after the median last frost.

How much rain and snow does 84540 get?

About 20.9 inches of precipitation a year (NOAA 1991–2020 normals, East Willow Creek station).

How hot do summers get in Thompson, UT?

The average high peaks at 101 °F in July, with about 104 days a year at 90 °F or more.

What kind of soil does 84540 have?

The USDA soil survey maps Shalako at the center of ZIP 84540: sandy loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Thompson, UT in 2026?

Spring leaf-out near 84540 came on Mar 17 in 2026, 18 days earlier than the 1991–2020 average (Apr 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Thompson, UT?

Intermediate onions: the longest day near 84540 is 14 h 56 min, so day-neutral types bulb best; long-day varieties may not bulb fully.