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

Planting zone for 84331 — Portage, UT

ZIP code 84331 (Portage, Box Elder County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 22 and the first fall frost September 20.

Where ZIP 84331 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 22
First frostSep 20
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 Portage, 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 Portage, UT

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 22median — 50% chance of a later frost
Safe for tender plantsJune 16only 10% chance of frost after
First fall frostSeptember 20median — 10% chance by Sep 4
Growing season116 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 4 and returns around October 2.

From the NOAA station Malad City, ID — 15 miles away, elevation 4,472 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 84331

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 10 – Apr 24
SpinachSow outdoors · Apr 10 – May 1
Broccoli, cabbageStart indoors · Mar 13 – Mar 27
Broccoli, cabbageTransplant · May 1 – May 15
Onion setsPlant outdoors · Apr 24 – May 8
PotatoesPlant outdoors · May 1 – May 15
LettuceSow outdoors · Apr 24 – May 8
Carrots, beetsSow outdoors · May 1 – May 15
TomatoesStart indoors · Mar 27 – Apr 10
TomatoesTransplant · May 29 – Jun 12
Peppers, eggplantStart indoors · Mar 13 – Mar 27
Peppers, eggplantTransplant · Jun 5 – Jun 19
BeansSow outdoors · May 29 – Jun 12
Sweet cornSow outdoors · May 29 – Jun 12
Cucumbers, squashSow outdoors · May 29 – Jun 12
Fall lettuce, spinachSow outdoors · Jul 26 – Aug 9
GarlicPlant cloves · Sep 6 – Oct 11
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 22) and first fall frost (Sep 20) 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 84331 came on Mar 27 — 21 days earlier than the 1991–2020 average (Apr 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).

Soil in Portage, UT

The soil mapped at the center of ZIP 84331 is Middle — cobbly silt loam, well drained.

TextureCobbly silt loama good balance for most vegetables
pH7.5slightly alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter4%moderate
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Middle cobbly silt loam, 30 to 70 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 84331; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Portage, UT

Summer high91 °Faverage high, July
Winter low15 °Faverage low, January
Hot days46days a year at 90 °F or more
Freezing nights185nights a year at 32 °F or less
Growing degree days2,221base 50 °F — the season’s usable heat
Longest day15 h 14 mindaylight on June 21
Shortest day9 h 07 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation14.7 inper year, rain and melted snow
Snowfall8 inper year

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 33 °F, low 15 °F 33°15° JanFebruary: average high 38 °F, low 18 °F 38°18° FebMarch: average high 51 °F, low 27 °F 51°27° MarApril: average high 60 °F, low 32 °F 60°32° AprMay: average high 70 °F, low 39 °F 70°39° MayJune: average high 80 °F, low 46 °F 80°46° JunJuly: average high 91 °F, low 51 °F 91°51° JulAugust: average high 88 °F, low 50 °F 88°50° AugSeptember: average high 78 °F, low 41 °F 78°41° SepOctober: average high 63 °F, low 32 °F 63°32° OctNovember: average high 47 °F, low 23 °F 47°23° NovDecember: average high 34 °F, low 16 °F 34°16° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 1.68 in precipitation, 2.5 in snowfall 1.7❄3 JanFebruary: 1.38 in precipitation, 1.8 in snowfall 1.4❄2 FebMarch: 1.39 in precipitation, 0.6 in snowfall 1.4❄1 MarApril: 1.33 in precipitation, 0.4 in snowfall 1.3 AprMay: 1.88 in precipitation, 0.1 in snowfall 1.9 MayJune: 0.90 in precipitation 0.9 JunJuly: 0.43 in precipitation 0.4 JulAugust: 0.59 in precipitation 0.6 AugSeptember: 1.28 in precipitation 1.3 SepOctober: 1.30 in precipitation, 0.2 in snowfall 1.3 OctNovember: 0.97 in precipitation, 0.3 in snowfall 1.0 NovDecember: 1.55 in precipitation, 1.6 in snowfall 1.6❄2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Malad City, ID (15 mi away); precipitation: Plymouth, UT (12 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.

843306a
Plymouth, UT · 10 mi
843166a
Howell, UT · 12 mi
843346b
Riverside, UT · 15 mi
843056a
Clarkston, UT · 15 mi
843116a
Fielding, UT · 15 mi
843126b
Garland, UT · 16 mi
832526a
Malad City, ID · 16 mi
843376b
Tremonton, UT · 18 mi

Utah planting zones →

Questions about 84331

What planting zone is ZIP code 84331?

ZIP code 84331 (Portage, 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 Portage, UT?

The median last spring frost (32 °F) near 84331 is May 22; after June 16 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Malad City station.

When is the first frost in Portage, UT?

The median first fall frost near 84331 is September 20, giving a median frost-free growing season of 116 days.

When should I plant tomatoes in 84331?

Start tomato seeds indoors around Mar 27 – Apr 10 and set transplants outside around May 29 – Jun 12, one to three weeks after the median last frost.

How much rain and snow does 84331 get?

About 14.7 inches of precipitation a year and 8 inches of snowfall (NOAA 1991–2020 normals, Plymouth station).

How hot do summers get in Portage, UT?

The average high peaks at 91 °F in July, with about 46 days a year at 90 °F or more.

What kind of soil does 84331 have?

The USDA soil survey maps Middle at the center of ZIP 84331: cobbly silt loam, well drained, pH about 7.5 (slightly alkaline).

Did spring come early in Portage, UT in 2026?

Spring leaf-out near 84331 came on Mar 27 in 2026, 21 days earlier than the 1991–2020 average (Apr 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Portage, UT?

Long-day onions: the longest day near 84331 is 15 h 14 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).