Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 30, 2026

Planting zone for 83450 — Terreton, ID

ZIP code 83450 (Terreton, Jefferson County) is in USDA zone 4b: the coldest winter night averages −25 to −20 °F. The median last spring frost is June 3 and the first fall frost September 11.

Where ZIP 83450 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.

Zone4b−25 to −20 °F

Coldest night−31.7 to −28.9 °C

Last frostJun 3

First frostSep 11

2012 zone4b

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 4b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Terreton, 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 Terreton, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostJune 3median — 50% chance of a later frost

Safe for tender plantsJune 21only 10% chance of frost after

First fall frostSeptember 11median — 10% chance by Aug 30

Growing season98 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 14 and returns around September 21.

From the NOAA station Hamer 4 Nw, ID — 11 miles away, elevation 4,790 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 83450

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 22 – May 6

SpinachSow outdoors · Apr 22 – May 13

Broccoli, cabbageStart indoors · Mar 25 – Apr 8

Broccoli, cabbageTransplant · May 13 – May 27

Onion setsPlant outdoors · May 6 – May 20

PotatoesPlant outdoors · May 13 – May 27

LettuceSow outdoors · May 6 – May 20

Carrots, beetsSow outdoors · May 13 – May 27

TomatoesStart indoors · Apr 8 – Apr 22

TomatoesTransplant · Jun 10 – Jun 24

Peppers, eggplantStart indoors · Mar 25 – Apr 8

Peppers, eggplantTransplant · Jun 17 – Jul 1

BeansSow outdoors · Jun 10 – Jun 24

Sweet cornSow outdoors · Jun 10 – Jun 24

Cucumbers, squashSow outdoors · Jun 10 – Jun 24

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 3) 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 83450 came on Mar 28 — 20 days earlier than the 1991–2020 average (Apr 17).

average
Apr 172026
Mar 28

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 4b in Idaho

478 plants native to the lower 48 states, recorded in Idaho, and rated by the USDA to survive −25 °F or colder — the bottom of zone 4b. 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 Terreton, ID.

Soil in Terreton, ID

The soil mapped at the center of ZIP 83450 is Terreton — silty clay loam, well drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up

pH8.2alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter0.75%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classFarmland of statewide importance, if irrigatedUSDA classification

Map unit: Terreton silty clay loam.

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 83450; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Terreton, ID

Summer high89 °Faverage high, July

Winter low7 °Faverage low, January

Hot days31days a year at 90 °F or more

Freezing nights205nights a year at 32 °F or less

Growing degree days1,964base 50 °F — the season’s usable heat

Longest day15 h 28 mindaylight on June 21

Shortest day8 h 54 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation8.9 inper year, rain and melted snow

Snowfall20 inper year; 69 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Hamer 4 Nw, ID (11 mi away); precipitation: Hamer 4 Nw, ID (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Monteview, ID · 13 mi

834345a

Menan, ID · 20 mi

834315a

Lewisville, ID · 21 mi

834025b

Idaho Falls, ID · 24 mi

Idaho planting zones →

Questions about 83450

What planting zone is ZIP code 83450?

ZIP code 83450 (Terreton, ID) is in USDA hardiness zone 4b on the 2023 map: the coldest night of an average winter reaches −25 to −20 °F (−31.7 to −28.9 °C).

When is the last frost in Terreton, ID?

The median last spring frost (32 °F) near 83450 is June 3; after June 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Hamer 4 Nw station.

When is the first frost in Terreton, ID?

The median first fall frost near 83450 is September 11, giving a median frost-free growing season of 98 days.

When should I plant tomatoes in 83450?

Start tomato seeds indoors around Apr 8 – Apr 22 and set transplants outside around Jun 10 – Jun 24, one to three weeks after the median last frost.

How much rain and snow does 83450 get?

About 8.9 inches of precipitation a year and 20 inches of snowfall (NOAA 1991–2020 normals, Hamer 4 Nw station).

How hot do summers get in Terreton, ID?

The average high peaks at 89 °F in July, with about 31 days a year at 90 °F or more.

What kind of soil does 83450 have?

The USDA soil survey maps Terreton at the center of ZIP 83450: silty clay loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Terreton, ID in 2026?

Spring leaf-out near 83450 came on Mar 28 in 2026, 20 days earlier than the 1991–2020 average (Apr 17), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Terreton, ID?

Long-day onions: the longest day near 83450 is 15 h 28 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).