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

Planting zone for 83645 — Midvale, ID

ZIP code 83645 (Midvale, Washington County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 15 and the first fall frost September 27.

Where ZIP 83645 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 15

First frostSep 27

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 Midvale, 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 Midvale, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 15median — 50% chance of a later frost

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

First fall frostSeptember 27median — 10% chance by Sep 12

Growing season134 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 28 and returns around October 7.

From the NOAA station Cambridge, ID — 17 miles away, elevation 2,651 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 83645

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 3 – Apr 17

SpinachSow outdoors · Apr 3 – Apr 24

Broccoli, cabbageStart indoors · Mar 6 – Mar 20

Broccoli, cabbageTransplant · Apr 24 – May 8

Onion setsPlant outdoors · Apr 17 – May 1

PotatoesPlant outdoors · Apr 24 – May 8

LettuceSow outdoors · Apr 17 – May 1

Carrots, beetsSow outdoors · Apr 24 – May 8

TomatoesStart indoors · Mar 20 – Apr 3

TomatoesTransplant · May 22 – Jun 5

Peppers, eggplantStart indoors · Mar 6 – Mar 20

Peppers, eggplantTransplant · May 29 – Jun 12

BeansSow outdoors · May 22 – Jun 5

Sweet cornSow outdoors · May 22 – Jun 5

Cucumbers, squashSow outdoors · May 22 – Jun 5

Fall lettuce, spinachSow outdoors · Aug 2 – Aug 16

GarlicPlant cloves · Sep 13 – Oct 18

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 15) and first fall frost (Sep 27) 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 83645 came on Mar 21 — 16 days earlier than the 1991–2020 average (Apr 6).

average
Apr 62026
Mar 21

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 Midvale, ID.

Soil in Midvale, ID

The soil mapped at the center of ZIP 83645 is Gem — very stony clay loam, well drained.

TextureVery stony clay loamholds water and nutrients; slow to drain and warm up

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3%moderate

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Gem-Reywat complex, stony surface, 2 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 83645; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Midvale, ID

Summer high93 °Faverage high, July

Winter low17 °Faverage low, January

Hot days62days a year at 90 °F or more

Freezing nights157nights a year at 32 °F or less

Growing degree days2,632base 50 °F — the season’s usable heat

Longest day15 h 32 mindaylight on June 21

Shortest day8 h 51 mindaylight on December 21

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

Precipitation26.8 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: Cambridge, ID (17 mi away); precipitation: Van Wyck, ID (12 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

836577a

Ola, ID · 15 mi

836326a

Indian Valley, ID · 15 mi

Idaho planting zones →

Questions about 83645

What planting zone is ZIP code 83645?

ZIP code 83645 (Midvale, 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 Midvale, ID?

The median last spring frost (32 °F) near 83645 is May 15; after June 4 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Cambridge station.

When is the first frost in Midvale, ID?

The median first fall frost near 83645 is September 27, giving a median frost-free growing season of 134 days.

When should I plant tomatoes in 83645?

Start tomato seeds indoors around Mar 20 – Apr 3 and set transplants outside around May 22 – Jun 5, one to three weeks after the median last frost.

How much rain and snow does 83645 get?

About 26.8 inches of precipitation a year (NOAA 1991–2020 normals, Van Wyck station).

How hot do summers get in Midvale, ID?

The average high peaks at 93 °F in July, with about 62 days a year at 90 °F or more.

What kind of soil does 83645 have?

The USDA soil survey maps Gem at the center of ZIP 83645: very stony clay loam, well drained, pH about 7.0 (neutral).

Did spring come early in Midvale, ID in 2026?

Spring leaf-out near 83645 came on Mar 21 in 2026, 16 days earlier than the 1991–2020 average (Apr 6), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Midvale, ID?

Long-day onions: the longest day near 83645 is 15 h 32 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).