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

Planting zone for 83340 — Ketchum, ID

ZIP code 83340 (Ketchum, Blaine County) is in USDA zone 5b: the coldest winter night averages −15 to −10 °F. The median last spring frost is May 13 and the first fall frost October 2.

Where ZIP 83340 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 13

First frostOct 2

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 Ketchum, 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 Ketchum, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 13median — 50% chance of a later frost

Safe for tender plantsJune 3only 10% chance of frost after

First fall frostOctober 2median — 10% chance by Sep 15

Growing season139 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 28 and returns around October 14.

From the NOAA station Bellevue, ID — 25 miles away, elevation 5,194 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 83340

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 1 – Apr 15

SpinachSow outdoors · Apr 1 – Apr 22

Broccoli, cabbageStart indoors · Mar 4 – Mar 18

Broccoli, cabbageTransplant · Apr 22 – May 6

Onion setsPlant outdoors · Apr 15 – Apr 29

PotatoesPlant outdoors · Apr 22 – May 6

LettuceSow outdoors · Apr 15 – Apr 29

Carrots, beetsSow outdoors · Apr 22 – May 6

TomatoesStart indoors · Mar 18 – Apr 1

TomatoesTransplant · May 20 – Jun 3

Peppers, eggplantStart indoors · Mar 4 – Mar 18

Peppers, eggplantTransplant · May 27 – Jun 10

BeansSow outdoors · May 20 – Jun 3

Sweet cornSow outdoors · May 20 – Jun 3

Cucumbers, squashSow outdoors · May 20 – Jun 3

Fall lettuce, spinachSow outdoors · Aug 7 – Aug 21

GarlicPlant cloves · Sep 18 – Oct 23

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 13) and first fall frost (Oct 2) 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 83340 came on Apr 27 — 16 days earlier than the 1991–2020 average (May 13).

average
May 132026
Apr 27

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 Ketchum, ID.

Soil in Ketchum, ID

The soil mapped at the center of ZIP 83340 is Xeric Humicryepts family — 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 groupAwater soaks in fast

Farmland classNot prime farmlandUSDA classification

Map unit: Xeric Humicryepts-Pachic Haploxerolls-Typic Haplocryepts families complex, 20 to 65 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 83340; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Ketchum, ID

Summer high80 °Faverage high, July

Winter low8 °Faverage low, January

Hot days4days a year at 90 °F or more

Freezing nights229nights a year at 32 °F or less

Growing degree days1,127base 50 °F — the season’s usable heat

Longest day15 h 27 mindaylight on June 21

Shortest day8 h 55 mindaylight on December 21

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

Precipitation22.5 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Ketchum Rs, ID (12 mi away); precipitation: Chocolate Gulch, ID (9 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.

833535b

Sun Valley, ID · 13 mi

833545b

Sun Valley, ID · 14 mi

833276a

Fairfield, ID · 19 mi

Idaho planting zones →

Questions about 83340

What planting zone is ZIP code 83340?

ZIP code 83340 (Ketchum, 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 Ketchum, ID?

The median last spring frost (32 °F) near 83340 is May 13; after June 3 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Bellevue station.

When is the first frost in Ketchum, ID?

The median first fall frost near 83340 is October 2, giving a median frost-free growing season of 139 days.

When should I plant tomatoes in 83340?

Start tomato seeds indoors around Mar 18 – Apr 1 and set transplants outside around May 20 – Jun 3, one to three weeks after the median last frost.

How much rain and snow does 83340 get?

About 22.5 inches of precipitation a year (NOAA 1991–2020 normals, Chocolate Gulch station).

How hot do summers get in Ketchum, ID?

The average high peaks at 80 °F in July, with about 4 days a year at 90 °F or more.

What kind of soil does 83340 have?

The USDA soil survey maps Xeric Humicryepts family at the center of ZIP 83340: slightly decomposed plant material, well drained, pH about 5.0 (strongly acidic).

Did spring come early in Ketchum, ID in 2026?

Spring leaf-out near 83340 came on Apr 27 in 2026, 16 days earlier than the 1991–2020 average (May 13), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Ketchum, ID?

Long-day onions: the longest day near 83340 is 15 h 27 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).