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

Planting zone for 84643 — Mayfield, UT

ZIP code 84643 (Mayfield, Sanpete County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 11 and the first fall frost October 6.

Where ZIP 84643 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.

Zone6a−10 to −5 °F

Coldest night−23.3 to −20.6 °C

Last frostMay 11

First frostOct 6

2012 zone6a

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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mayfield, 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 Mayfield, UT

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 11median — 50% chance of a later frost

Safe for tender plantsJune 1only 10% chance of frost after

First fall frostOctober 6median — 10% chance by Sep 24

Growing season146 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 26 and returns around October 16.

From the NOAA station Manti, UT — 9 miles away, elevation 5,742 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 84643

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 30 – Apr 13

SpinachSow outdoors · Mar 30 – Apr 20

Broccoli, cabbageStart indoors · Mar 2 – Mar 16

Broccoli, cabbageTransplant · Apr 20 – May 4

Onion setsPlant outdoors · Apr 13 – Apr 27

PotatoesPlant outdoors · Apr 20 – May 4

LettuceSow outdoors · Apr 13 – Apr 27

Carrots, beetsSow outdoors · Apr 20 – May 4

TomatoesStart indoors · Mar 16 – Mar 30

TomatoesTransplant · May 18 – Jun 1

Peppers, eggplantStart indoors · Mar 2 – Mar 16

Peppers, eggplantTransplant · May 25 – Jun 8

BeansSow outdoors · May 18 – Jun 1

Sweet cornSow outdoors · May 18 – Jun 1

Cucumbers, squashSow outdoors · May 18 – Jun 1

Fall lettuce, spinachSow outdoors · Aug 11 – Aug 25

GarlicPlant cloves · Sep 22 – Oct 27

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 11) and first fall frost (Oct 6) 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 84643 came on Mar 16 — 22 days earlier than the 1991–2020 average (Apr 7).

average
Apr 72026
Mar 16

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 6a in Utah

546 plants native to the lower 48 states, recorded in Utah, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. 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 Mayfield, UT.

Soil in Mayfield, UT

The soil mapped at the center of ZIP 84643 is Borvant — cobbly loam, well drained.

TextureCobbly loama good balance for most vegetables

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: Borvant-Lodar complex, 8 to 25 percent slopes, eroded.

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 84643; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mayfield, UT

Summer high87 °Faverage high, July

Winter low19 °Faverage low, January

Hot days18days a year at 90 °F or more

Freezing nights167nights a year at 32 °F or less

Growing degree days2,504base 50 °F — the season’s usable heat

Longest day14 h 55 mindaylight on June 21

Shortest day9 h 25 mindaylight on December 21

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

Precipitation26.1 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: Manti, UT (9 mi away); precipitation: Beaver Dams, UT (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

846656a

Sterling, UT · 6 mi

846226a

Centerfield, UT · 7 mi

Utah planting zones →

Questions about 84643

What planting zone is ZIP code 84643?

ZIP code 84643 (Mayfield, UT) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Mayfield, UT?

The median last spring frost (32 °F) near 84643 is May 11; after June 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Manti station.

When is the first frost in Mayfield, UT?

The median first fall frost near 84643 is October 6, giving a median frost-free growing season of 146 days.

When should I plant tomatoes in 84643?

Start tomato seeds indoors around Mar 16 – Mar 30 and set transplants outside around May 18 – Jun 1, one to three weeks after the median last frost.

How much rain and snow does 84643 get?

About 26.1 inches of precipitation a year (NOAA 1991–2020 normals, Beaver Dams station).

How hot do summers get in Mayfield, UT?

The average high peaks at 87 °F in July, with about 18 days a year at 90 °F or more.

What kind of soil does 84643 have?

The USDA soil survey maps Borvant at the center of ZIP 84643: cobbly loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Mayfield, UT in 2026?

Spring leaf-out near 84643 came on Mar 16 in 2026, 22 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mayfield, UT?

Intermediate onions: the longest day near 84643 is 14 h 55 min, so day-neutral types bulb best; long-day varieties may not bulb fully.