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

Planting zone for 83402 — Idaho Falls, ID

ZIP code 83402 (Idaho Falls, Bonneville County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 23 and the first fall frost September 20.

Where ZIP 83402 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.

Zone5b−15 to −10 °F
Coldest night−26.1 to −23.3 °C
Last frostMay 23
First frostSep 20
2012 zone5a

Was 5a on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Idaho Falls, ID…

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 Idaho Falls, ID

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMay 23median — 50% chance of a later frost
Safe for tender plantsJune 13only 10% chance of frost after
First fall frostSeptember 20median — 10% chance by Sep 1
Growing season114 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 7 and returns around October 2.

From the NOAA station Idaho Falls Fanning Field, ID — 6 miles away, elevation 4,728 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 83402

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 11 – Apr 25
SpinachSow outdoors · Apr 11 – May 2
Broccoli, cabbageStart indoors · Mar 14 – Mar 28
Broccoli, cabbageTransplant · May 2 – May 16
Onion setsPlant outdoors · Apr 25 – May 9
PotatoesPlant outdoors · May 2 – May 16
LettuceSow outdoors · Apr 25 – May 9
Carrots, beetsSow outdoors · May 2 – May 16
TomatoesStart indoors · Mar 28 – Apr 11
TomatoesTransplant · May 30 – Jun 13
Peppers, eggplantStart indoors · Mar 14 – Mar 28
Peppers, eggplantTransplant · Jun 6 – Jun 20
BeansSow outdoors · May 30 – Jun 13
Sweet cornSow outdoors · May 30 – Jun 13
Cucumbers, squashSow outdoors · May 30 – Jun 13
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 23) 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 83402 came on Mar 24 — 24 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).

Native plants for zone 5b in Idaho

553 plants native to the lower 48 states, recorded in Idaho, and rated by the USDA to survive −15 °F or colder — the bottom of zone 5b. Each links to its USDA PLANTS profile.

Trees 30

balsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fblue spruce100 ft · blooms late spring · medium shade tolerance · to −38 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °FDouglas-fir200 ft · blooms mid spring · medium shade tolerance · to −33 °FEngelmann spruce120 ft · blooms late spring · low shade tolerance · to −50 °F

Shrubs 94

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 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °FBarclay's willow15 ft · high shade tolerance · to −43 °Fbeaked hazelnut15 ft · blooms early spring · low shade tolerance · to −47 °F

Wildflowers & perennials 267

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 eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °F

Grasses 151

Alaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali 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 °F

Vines 1

western 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 Idaho Falls, ID.

Soil in Idaho Falls, ID

The soil mapped at the center of ZIP 83402 is Pancheri — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH7.9alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classNot prime farmlandUSDA classification

Map unit: Pancheri-Rock outcrop complex, 2 to 25 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 83402; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Idaho Falls, ID

Summer high87 °Faverage high, July
Winter low12 °Faverage low, January
Hot days26days a year at 90 °F or more
Freezing nights182nights a year at 32 °F or less
Growing degree days1,843base 50 °F — the season’s usable heat
Longest day15 h 26 mindaylight on June 21
Shortest day8 h 56 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation10.1 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 29 °F, low 12 °F 29°12° JanFebruary: average high 34 °F, low 16 °F 34°16° FebMarch: average high 47 °F, low 25 °F 47°25° MarApril: average high 58 °F, low 31 °F 58°31° AprMay: average high 67 °F, low 38 °F 67°38° MayJune: average high 76 °F, low 45 °F 76°45° JunJuly: average high 87 °F, low 49 °F 87°49° JulAugust: average high 86 °F, low 48 °F 86°48° AugSeptember: average high 75 °F, low 41 °F 75°41° SepOctober: average high 59 °F, low 31 °F 59°31° OctNovember: average high 43 °F, low 22 °F 43°22° NovDecember: average high 30 °F, low 13 °F 30°13° Dec

Precipitation by month inches

0″1″2″January: 0.67 in precipitation 0.7 JanFebruary: 0.56 in precipitation 0.6 FebMarch: 0.81 in precipitation 0.8 MarApril: 1.03 in precipitation 1.0 AprMay: 1.57 in precipitation 1.6 MayJune: 1.09 in precipitation 1.1 JunJuly: 0.46 in precipitation 0.5 JulAugust: 0.59 in precipitation 0.6 AugSeptember: 0.97 in precipitation 1.0 SepOctober: 0.88 in precipitation 0.9 OctNovember: 0.66 in precipitation 0.7 NovDecember: 0.78 in precipitation 0.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Idaho Falls Fanning Field, ID (6 mi away); precipitation: Idaho Falls Fanning Field, ID (6 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.

834035b
Idaho Falls, ID · 8 mi
834055b
Idaho Falls, ID · 8 mi
834155b
Idaho Falls, ID · 8 mi
834045b
Idaho Falls, ID · 11 mi
832745b
Shelley, ID · 13 mi
834315a
Lewisville, ID · 13 mi
834065b
Idaho Falls, ID · 14 mi
832185b
Basalt, ID · 14 mi

All 7 ZIP codes in Idaho Falls → · Idaho planting zones →

Questions about 83402

What planting zone is ZIP code 83402?

ZIP code 83402 (Idaho Falls, ID) is in USDA hardiness zone 5b on the 2023 map: the coldest night of an average winter reaches −15 to −10 °F (−26.1 to −23.3 °C).

When is the last frost in Idaho Falls, ID?

The median last spring frost (32 °F) near 83402 is May 23; after June 13 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Idaho Falls Fanning Field station.

When is the first frost in Idaho Falls, ID?

The median first fall frost near 83402 is September 20, giving a median frost-free growing season of 114 days.

When should I plant tomatoes in 83402?

Start tomato seeds indoors around Mar 28 – Apr 11 and set transplants outside around May 30 – Jun 13, one to three weeks after the median last frost.

How much rain and snow does 83402 get?

About 10.1 inches of precipitation a year (NOAA 1991–2020 normals, Idaho Falls Fanning Field station).

How hot do summers get in Idaho Falls, ID?

The average high peaks at 87 °F in July, with about 26 days a year at 90 °F or more.

What kind of soil does 83402 have?

The USDA soil survey maps Pancheri at the center of ZIP 83402: silt loam, well drained, pH about 7.9 (alkaline).

Did spring come early in Idaho Falls, ID in 2026?

Spring leaf-out near 83402 came on Mar 24 in 2026, 24 days earlier than the 1991–2020 average (Apr 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Idaho Falls, ID?

Long-day onions: the longest day near 83402 is 15 h 26 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 83402 change?

Yes. The 2012 USDA map put 83402 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.