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

Planting zone for 84631 — Fillmore, UT

ZIP code 84631 (Fillmore, Millard County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 4 and the first fall frost October 14.

Where ZIP 84631 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 4
First frostOct 14
2012 zone6b

Was 6b on the 2012 map — half a zone colder now. 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 Fillmore, 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 Fillmore, UT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 4median — 50% chance of a later frost
Safe for tender plantsMay 26only 10% chance of frost after
First fall frostOctober 14median — 10% chance by Sep 30
Growing season160 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 19 and returns around October 25.

From the NOAA station Fillmore, UT — 5 miles away, elevation 5,128 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 84631

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 23 – Apr 6
SpinachSow outdoors · Mar 23 – Apr 13
Broccoli, cabbageStart indoors · Feb 23 – Mar 9
Broccoli, cabbageTransplant · Apr 13 – Apr 27
Onion setsPlant outdoors · Apr 6 – Apr 20
PotatoesPlant outdoors · Apr 13 – Apr 27
LettuceSow outdoors · Apr 6 – Apr 20
Carrots, beetsSow outdoors · Apr 13 – Apr 27
TomatoesStart indoors · Mar 9 – Mar 23
TomatoesTransplant · May 11 – May 25
Peppers, eggplantStart indoors · Feb 23 – Mar 9
Peppers, eggplantTransplant · May 18 – Jun 1
BeansSow outdoors · May 11 – May 25
Sweet cornSow outdoors · May 11 – May 25
Cucumbers, squashSow outdoors · May 11 – May 25
Fall lettuce, spinachSow outdoors · Aug 19 – Sep 2
GarlicPlant cloves · Sep 30 – Nov 4
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 4) and first fall frost (Oct 14) 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 84631 came on Mar 7 — 15 days earlier than the 1991–2020 average (Mar 22).

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.

Trees 30

American beech80 ft · blooms mid spring · low shade tolerance · to −44 °FArizona cypress50 ft · blooms spring · low shade tolerance · to −23 °FArizona walnut50 ft · blooms late spring · high shade tolerance · to −33 °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 °F

Shrubs 107

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °Falderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °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 248

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °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 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °F

Grasses 151

alkali 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 °Farctic bluegrass2 ft · high shade tolerance · to −62 °F

Vines 3

trumpet creeper2 ft · blooms summer · high shade tolerance · to −13 °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 Fillmore, UT.

Soil in Fillmore, UT

The soil mapped at the center of ZIP 84631 is Escalante — 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 matter0.75%low — add compost
Hydrologic groupAwater soaks in fast
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Escalante sandy loam, 2 to 5 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 84631; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fillmore, UT

Summer high88 °Faverage high, July
Winter low21 °Faverage low, January
Hot days37days a year at 90 °F or more
Freezing nights138nights a year at 32 °F or less
Growing degree days3,004base 50 °F — the season’s usable heat
Longest day14 h 54 mindaylight on June 21
Shortest day9 h 26 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation15 inper year, rain and melted snow
Snowfall62 inper year

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 38 °F, low 21 °F 38°21° JanFebruary: average high 45 °F, low 25 °F 45°25° FebMarch: average high 55 °F, low 32 °F 55°32° MarApril: average high 62 °F, low 37 °F 62°37° AprMay: average high 72 °F, low 45 °F 72°45° MayJune: average high 82 °F, low 53 °F 82°53° JunJuly: average high 88 °F, low 60 °F 88°60° JulAugust: average high 86 °F, low 60 °F 86°60° AugSeptember: average high 78 °F, low 51 °F 78°51° SepOctober: average high 64 °F, low 39 °F 64°39° OctNovember: average high 50 °F, low 29 °F 50°29° NovDecember: average high 38 °F, low 21 °F 38°21° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 1.32 in precipitation, 11.9 in snowfall 1.3❄12 JanFebruary: 1.37 in precipitation, 13.2 in snowfall 1.4❄13 FebMarch: 1.65 in precipitation, 7.9 in snowfall 1.6❄8 MarApril: 1.68 in precipitation, 5.1 in snowfall 1.7❄5 AprMay: 1.53 in precipitation, 0.3 in snowfall 1.5 MayJune: 0.67 in precipitation 0.7 JunJuly: 0.79 in precipitation 0.8 JulAugust: 0.80 in precipitation 0.8 AugSeptember: 0.99 in precipitation, 0.1 in snowfall 1.0 SepOctober: 1.48 in precipitation, 2.9 in snowfall 1.5❄3 OctNovember: 1.29 in precipitation, 8.2 in snowfall 1.3❄8 NovDecember: 1.47 in precipitation, 12.4 in snowfall 1.5❄12 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Fillmore, UT (5 mi away); precipitation: Fillmore, UT (5 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.

846366a
Holden, UT · 10 mi
846446b
Meadow, UT · 11 mi
846376b
Kanosh, UT · 20 mi
846565b
Scipio, UT · 23 mi
847246a
Elsinore, UT · 26 mi
847396a
Joseph, UT · 26 mi
847116a
Annabella, UT · 27 mi
847306a
Glenwood, UT · 27 mi

Utah planting zones →

Questions about 84631

What planting zone is ZIP code 84631?

ZIP code 84631 (Fillmore, 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 Fillmore, UT?

The median last spring frost (32 °F) near 84631 is May 4; after May 26 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Fillmore station.

When is the first frost in Fillmore, UT?

The median first fall frost near 84631 is October 14, giving a median frost-free growing season of 160 days.

When should I plant tomatoes in 84631?

Start tomato seeds indoors around Mar 9 – Mar 23 and set transplants outside around May 11 – May 25, one to three weeks after the median last frost.

How much rain and snow does 84631 get?

About 15 inches of precipitation a year and 62 inches of snowfall (NOAA 1991–2020 normals, Fillmore station).

How hot do summers get in Fillmore, UT?

The average high peaks at 88 °F in July, with about 37 days a year at 90 °F or more.

What kind of soil does 84631 have?

The USDA soil survey maps Escalante at the center of ZIP 84631: sandy loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Fillmore, UT in 2026?

Spring leaf-out near 84631 came on Mar 7 in 2026, 15 days earlier than the 1991–2020 average (Mar 22), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Fillmore, UT?

Intermediate onions: the longest day near 84631 is 14 h 54 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 84631 change?

Yes. The 2012 USDA map put 84631 in zone 6b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.