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

Planting zone for 83821 — Coolin, ID

ZIP code 83821 (Coolin, Bonner County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 20 and the first fall frost September 13.

Where ZIP 83821 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 20

First frostSep 13

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 Coolin, 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 Coolin, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 20median — 50% chance of a later frost

Safe for tender plantsJune 4only 10% chance of frost after

First fall frostSeptember 13median — 10% chance by Sep 1

Growing season114 daysfrost-free, median

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

From the NOAA station Priest Rvr Exp Stn, ID — 12 miles away, elevation 2,372 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 83821

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 8 – Apr 22

SpinachSow outdoors · Apr 8 – Apr 29

Broccoli, cabbageStart indoors · Mar 11 – Mar 25

Broccoli, cabbageTransplant · Apr 29 – May 13

Onion setsPlant outdoors · Apr 22 – May 6

PotatoesPlant outdoors · Apr 29 – May 13

LettuceSow outdoors · Apr 22 – May 6

Carrots, beetsSow outdoors · Apr 29 – May 13

TomatoesStart indoors · Mar 25 – Apr 8

TomatoesTransplant · May 27 – Jun 10

Peppers, eggplantStart indoors · Mar 11 – Mar 25

Peppers, eggplantTransplant · Jun 3 – Jun 17

BeansSow outdoors · May 27 – Jun 10

Sweet cornSow outdoors · May 27 – Jun 10

Cucumbers, squashSow outdoors · May 27 – Jun 10

Fall lettuce, spinachSow outdoors · Jul 19 – Aug 2

GarlicPlant cloves · Aug 30 – Oct 4

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 20) and first fall frost (Sep 13) 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 83821 came on Apr 12 — 9 days earlier than the 1991–2020 average (Apr 21).

average
Apr 212026
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 6a in Idaho

567 plants native to the lower 48 states, recorded in Idaho, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. 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 Coolin, ID.

Soil in Coolin, ID

The soil mapped at the center of ZIP 83821 is Elmira variant — slightly decomposed plant material, poorly drained.

TextureSlightly decomposed plant materialtop layer

pH5.0strongly acidic; most vegetables like 6.0–7.0

DrainagePoorly drainedconsider raised beds

Organic matter75%high

Hydrologic groupAwater soaks in fast

Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Elmira variant loamy coarse sand, 0 to 2 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 83821; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Coolin, ID

Summer high83 °Faverage high, July

Winter low22 °Faverage low, January

Hot days17days a year at 90 °F or more

Freezing nights190nights a year at 32 °F or less

Growing degree days1,559base 50 °F — the season’s usable heat

Longest day16 h 08 mindaylight on June 21

Shortest day8 h 18 mindaylight on December 21

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

Precipitation32.6 inper year, rain and melted snow

Snowfall74 inper year; 114 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: Priest Rvr Exp Stn, ID (12 mi away); precipitation: Priest Rvr Exp Stn, ID (12 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

838566a

Priest River, ID · 13 mi

Sandpoint, ID · 17 mi

Idaho planting zones →

Questions about 83821

What planting zone is ZIP code 83821?

ZIP code 83821 (Coolin, ID) 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 Coolin, ID?

The median last spring frost (32 °F) near 83821 is May 20; after June 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Priest Rvr Exp Stn station.

When is the first frost in Coolin, ID?

The median first fall frost near 83821 is September 13, giving a median frost-free growing season of 114 days.

When should I plant tomatoes in 83821?

Start tomato seeds indoors around Mar 25 – Apr 8 and set transplants outside around May 27 – Jun 10, one to three weeks after the median last frost.

How much rain and snow does 83821 get?

About 32.6 inches of precipitation a year and 74 inches of snowfall (NOAA 1991–2020 normals, Priest Rvr Exp Stn station).

How hot do summers get in Coolin, ID?

The average high peaks at 83 °F in July, with about 17 days a year at 90 °F or more.

What kind of soil does 83821 have?

The USDA soil survey maps Elmira variant at the center of ZIP 83821: slightly decomposed plant material, poorly drained, pH about 5.0 (strongly acidic).

Did spring come early in Coolin, ID in 2026?

Spring leaf-out near 83821 came on Apr 12 in 2026, 9 days earlier than the 1991–2020 average (Apr 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Coolin, ID?

Long-day onions: the longest day near 83821 is 16 h 08 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).