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

Planting zone for 83643 — Mesa, ID

ZIP code 83643 (Mesa, Adams County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 10 and the first fall frost October 2.

Where ZIP 83643 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 10

First frostOct 2

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 Mesa, 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 Mesa, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 10median — 50% chance of a later frost

Safe for tender plantsJune 1only 10% chance of frost after

First fall frostOctober 2median — 10% chance by Sep 16

Growing season145 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 22 and returns around October 16.

From the NOAA station Council, ID — 8 miles away, elevation 2,943 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 83643

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 29 – Apr 12

SpinachSow outdoors · Mar 29 – Apr 19

Broccoli, cabbageStart indoors · Mar 1 – Mar 15

Broccoli, cabbageTransplant · Apr 19 – May 3

Onion setsPlant outdoors · Apr 12 – Apr 26

PotatoesPlant outdoors · Apr 19 – May 3

LettuceSow outdoors · Apr 12 – Apr 26

Carrots, beetsSow outdoors · Apr 19 – May 3

TomatoesStart indoors · Mar 15 – Mar 29

TomatoesTransplant · May 17 – May 31

Peppers, eggplantStart indoors · Mar 1 – Mar 15

Peppers, eggplantTransplant · May 24 – Jun 7

BeansSow outdoors · May 17 – May 31

Sweet cornSow outdoors · May 17 – May 31

Cucumbers, squashSow outdoors · May 17 – May 31

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 10) 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 83643 came on Mar 24 — 14 days earlier than the 1991–2020 average (Apr 7).

average
Apr 72026
Mar 24

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 Mesa, ID.

Soil in Mesa, ID

The soil mapped at the center of ZIP 83643 is Appledellia — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupDwater soaks in very slowly

Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Appledellia-Odermott complex, 4 to 8 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 83643; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mesa, ID

Summer high92 °Faverage high, July

Winter low18 °Faverage low, January

Hot days56days a year at 90 °F or more

Freezing nights159nights a year at 32 °F or less

Growing degree days2,684base 50 °F — the season’s usable heat

Longest day15 h 34 mindaylight on June 21

Shortest day8 h 49 mindaylight on December 21

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

Precipitation22.4 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: Council, ID (8 mi away); precipitation: Council, ID (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

836326a

Indian Valley, ID · 7 mi

836126a

Council, ID · 16 mi

836107a

Cambridge, ID · 17 mi

Lake Fork, ID · 23 mi

Idaho planting zones →

Questions about 83643

What planting zone is ZIP code 83643?

ZIP code 83643 (Mesa, 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 Mesa, ID?

The median last spring frost (32 °F) near 83643 is May 10; after June 1 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Council station.

When is the first frost in Mesa, ID?

The median first fall frost near 83643 is October 2, giving a median frost-free growing season of 145 days.

When should I plant tomatoes in 83643?

Start tomato seeds indoors around Mar 15 – Mar 29 and set transplants outside around May 17 – May 31, one to three weeks after the median last frost.

How much rain and snow does 83643 get?

About 22.4 inches of precipitation a year (NOAA 1991–2020 normals, Council station).

How hot do summers get in Mesa, ID?

The average high peaks at 92 °F in July, with about 56 days a year at 90 °F or more.

What kind of soil does 83643 have?

The USDA soil survey maps Appledellia at the center of ZIP 83643: clay loam, well drained, pH about 7.0 (neutral).

Did spring come early in Mesa, ID in 2026?

Spring leaf-out near 83643 came on Mar 24 in 2026, 14 days earlier than the 1991–2020 average (Apr 7), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mesa, ID?

Long-day onions: the longest day near 83643 is 15 h 34 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).