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

Planting zone for 83236 — Firth, ID

ZIP code 83236 (Firth, Bingham County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is June 9 and the first fall frost September 11.

Where ZIP 83236 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 frostJun 9
First frostSep 11
2012 zone5b

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 5b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Firth, 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 Firth, ID

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostJune 9median — 50% chance of a later frost
Safe for tender plantsJune 26only 10% chance of frost after
First fall frostSeptember 11median — 10% chance by Aug 27
Growing season93 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 19 and returns around September 23.

From the NOAA station Idaho Falls 16 Se, ID — 12 miles away, elevation 5,827 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 83236

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Apr 28 – May 12
SpinachSow outdoors · Apr 28 – May 19
Broccoli, cabbageStart indoors · Mar 31 – Apr 14
Broccoli, cabbageTransplant · May 19 – Jun 2
Onion setsPlant outdoors · May 12 – May 26
PotatoesPlant outdoors · May 19 – Jun 2
LettuceSow outdoors · May 12 – May 26
Carrots, beetsSow outdoors · May 19 – Jun 2
TomatoesStart indoors · Apr 14 – Apr 28
TomatoesTransplant · Jun 16 – Jun 30
Peppers, eggplantStart indoors · Mar 31 – Apr 14
Peppers, eggplantTransplant · Jun 23 – Jul 7
BeansSow outdoors · Jun 16 – Jun 30
Sweet cornSow outdoors · Jun 16 – Jun 30
Cucumbers, squashSow outdoors · Jun 16 – Jun 30
Fall lettuce, spinachSow outdoors · Jul 17 – Jul 31
GarlicPlant cloves · Aug 28 – Oct 2
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Jun 9) and first fall frost (Sep 11) 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 83236 came on Apr 7 — 26 days earlier than the 1991–2020 average (May 3).

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 Firth, ID

The soil mapped at the center of ZIP 83236 is Pavohroo — slightly decomposed plant material, well drained.

TextureSlightly decomposed plant materialtop layer
pH5.0strongly acidic; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter75%high
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Pavohroo loam, steep.

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 83236; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Firth, ID

Summer high81 °Faverage high, July
Winter low13 °Faverage low, December
Hot days6days a year at 90 °F or more
Freezing nights199nights a year at 32 °F or less
Growing degree days1,430base 50 °F — the season’s usable heat
Longest day15 h 23 mindaylight on June 21
Shortest day8 h 59 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation25.6 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°32 °FJanuary: average high 31 °F, low 14 °F 31°14° JanFebruary: average high 34 °F, low 15 °F 34°15° FebMarch: average high 42 °F, low 24 °F 42°24° MarApril: average high 51 °F, low 29 °F 51°29° AprMay: average high 62 °F, low 37 °F 62°37° MayJune: average high 71 °F, low 43 °F 71°43° JunJuly: average high 81 °F, low 50 °F 81°50° JulAugust: average high 79 °F, low 48 °F 79°48° AugSeptember: average high 70 °F, low 40 °F 70°40° SepOctober: average high 56 °F, low 30 °F 56°30° OctNovember: average high 41 °F, low 21 °F 41°21° NovDecember: average high 30 °F, low 13 °F 30°13° Dec

Precipitation by month inches

0″1″2″3″4″January: 3.38 in precipitation 3.4 JanFebruary: 2.51 in precipitation 2.5 FebMarch: 2.50 in precipitation 2.5 MarApril: 2.50 in precipitation 2.5 AprMay: 2.76 in precipitation 2.8 MayJune: 1.46 in precipitation 1.5 JunJuly: 0.73 in precipitation 0.7 JulAugust: 0.89 in precipitation 0.9 AugSeptember: 1.37 in precipitation 1.4 SepOctober: 1.75 in precipitation 1.8 OctNovember: 2.43 in precipitation 2.4 NovDecember: 3.33 in precipitation 3.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Idaho Falls 16 Se, ID (12 mi away); precipitation: Sheep Mtn., ID (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 5b.

834275b
Iona, ID · 13 mi
832745b
Shelley, ID · 16 mi
832185b
Basalt, ID · 17 mi
834065b
Idaho Falls, ID · 17 mi
834045b
Idaho Falls, ID · 18 mi
834035b
Idaho Falls, ID · 21 mi
834055b
Idaho Falls, ID · 21 mi
834155b
Idaho Falls, ID · 21 mi

Idaho planting zones →

Questions about 83236

What planting zone is ZIP code 83236?

ZIP code 83236 (Firth, 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 Firth, ID?

The median last spring frost (32 °F) near 83236 is June 9; after June 26 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Idaho Falls 16 Se station.

When is the first frost in Firth, ID?

The median first fall frost near 83236 is September 11, giving a median frost-free growing season of 93 days.

When should I plant tomatoes in 83236?

Start tomato seeds indoors around Apr 14 – Apr 28 and set transplants outside around Jun 16 – Jun 30, one to three weeks after the median last frost.

How much rain and snow does 83236 get?

About 25.6 inches of precipitation a year (NOAA 1991–2020 normals, Sheep Mtn. station).

How hot do summers get in Firth, ID?

The average high peaks at 81 °F in July, with about 6 days a year at 90 °F or more.

What kind of soil does 83236 have?

The USDA soil survey maps Pavohroo at the center of ZIP 83236: slightly decomposed plant material, well drained, pH about 5.0 (strongly acidic).

Did spring come early in Firth, ID in 2026?

Spring leaf-out near 83236 came on Apr 7 in 2026, 26 days earlier than the 1991–2020 average (May 3), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Firth, ID?

Long-day onions: the longest day near 83236 is 15 h 23 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).