Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 83446 — Spencer, ID

ZIP code 83446 (Spencer, Clark County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 18 and the first fall frost September 30.

Where ZIP 83446 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 18

First frostSep 30

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 Spencer, 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 Spencer, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 18median — 50% chance of a later frost

Safe for tender plantsJune 9only 10% chance of frost after

First fall frostSeptember 30median — 10% chance by Sep 14

Growing season132 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 2 and returns around October 12.

From the NOAA station Dubois Exp Stn, ID — 9 miles away, elevation 5,450 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 83446

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 6 – Apr 20

SpinachSow outdoors · Apr 6 – Apr 27

Broccoli, cabbageStart indoors · Mar 9 – Mar 23

Broccoli, cabbageTransplant · Apr 27 – May 11

Onion setsPlant outdoors · Apr 20 – May 4

PotatoesPlant outdoors · Apr 27 – May 11

LettuceSow outdoors · Apr 20 – May 4

Carrots, beetsSow outdoors · Apr 27 – May 11

TomatoesStart indoors · Mar 23 – Apr 6

TomatoesTransplant · May 25 – Jun 8

Peppers, eggplantStart indoors · Mar 9 – Mar 23

Peppers, eggplantTransplant · Jun 1 – Jun 15

BeansSow outdoors · May 25 – Jun 8

Sweet cornSow outdoors · May 25 – Jun 8

Cucumbers, squashSow outdoors · May 25 – Jun 8

Fall lettuce, spinachSow outdoors · Aug 5 – Aug 19

GarlicPlant cloves · Sep 16 – Oct 21

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 18) and first fall frost (Sep 30) 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 83446 came on Apr 12 — 20 days earlier than the 1991–2020 average (May 2).

average
May 22026
Apr 12

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.

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 Spencer, ID.

Soil in Spencer, ID

The soil mapped at the center of ZIP 83446 is Povey — gravelly loam, well drained.

TextureGravelly loama good balance for most vegetables

pH6.7neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter7%high

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Povey gravelly loam, 4 to 30 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 83446; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Spencer, ID

Summer high87 °Faverage high, July

Winter low15 °Faverage low, January

Hot days20days a year at 90 °F or more

Freezing nights178nights a year at 32 °F or less

Growing degree days2,158base 50 °F — the season’s usable heat

Longest day15 h 32 mindaylight on June 21

Shortest day8 h 50 mindaylight on December 21

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

Precipitation12.2 inper year, rain and melted snow

Snowfall47 inper year; 112 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: Dubois Exp Stn, ID (9 mi away); precipitation: Dubois Exp Stn, ID (9 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.

Saint Anthony, ID · 32 mi

834354b

Monteview, ID · 32 mi

Idaho planting zones →

Questions about 83446

What planting zone is ZIP code 83446?

ZIP code 83446 (Spencer, 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 Spencer, ID?

The median last spring frost (32 °F) near 83446 is May 18; after June 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Dubois Exp Stn station.

When is the first frost in Spencer, ID?

The median first fall frost near 83446 is September 30, giving a median frost-free growing season of 132 days.

When should I plant tomatoes in 83446?

Start tomato seeds indoors around Mar 23 – Apr 6 and set transplants outside around May 25 – Jun 8, one to three weeks after the median last frost.

How much rain and snow does 83446 get?

About 12.2 inches of precipitation a year and 47 inches of snowfall (NOAA 1991–2020 normals, Dubois Exp Stn station).

How hot do summers get in Spencer, ID?

The average high peaks at 87 °F in July, with about 20 days a year at 90 °F or more.

What kind of soil does 83446 have?

The USDA soil survey maps Povey at the center of ZIP 83446: gravelly loam, well drained, pH about 6.7 (neutral).

Did spring come early in Spencer, ID in 2026?

Spring leaf-out near 83446 came on Apr 12 in 2026, 20 days earlier than the 1991–2020 average (May 2), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Spencer, ID?

Long-day onions: the longest day near 83446 is 15 h 32 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 83446 change?

Yes. The 2012 USDA map put 83446 in zone 5a; the 2023 map puts it in zone 5b. The newer map uses 1991–2020 data and more weather stations.