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

Planting zone for 83243 — Holbrook, ID

ZIP code 83243 (Holbrook, Oneida County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is May 22 and the first fall frost September 20.

Where ZIP 83243 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 22

First frostSep 20

2012 zone5b

Was 5b 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 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Holbrook, 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 Holbrook, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 22median — 50% chance of a later frost

Safe for tender plantsJune 16only 10% chance of frost after

First fall frostSeptember 20median — 10% chance by Sep 4

Growing season116 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 4 and returns around October 2.

From the NOAA station Malad City, ID — 20 miles away, elevation 4,472 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 83243

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 10 – Apr 24

SpinachSow outdoors · Apr 10 – May 1

Broccoli, cabbageStart indoors · Mar 13 – Mar 27

Broccoli, cabbageTransplant · May 1 – May 15

Onion setsPlant outdoors · Apr 24 – May 8

PotatoesPlant outdoors · May 1 – May 15

LettuceSow outdoors · Apr 24 – May 8

Carrots, beetsSow outdoors · May 1 – May 15

TomatoesStart indoors · Mar 27 – Apr 10

TomatoesTransplant · May 29 – Jun 12

Peppers, eggplantStart indoors · Mar 13 – Mar 27

Peppers, eggplantTransplant · Jun 5 – Jun 19

BeansSow outdoors · May 29 – Jun 12

Sweet cornSow outdoors · May 29 – Jun 12

Cucumbers, squashSow outdoors · May 29 – Jun 12

Fall lettuce, spinachSow outdoors · Jul 26 – Aug 9

GarlicPlant cloves · Sep 6 – Oct 11

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 22) and first fall frost (Sep 20) 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 83243 came on Mar 23 — 23 days earlier than the 1991–2020 average (Apr 15).

average
Apr 152026
Mar 23

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 Holbrook, ID.

Soil in Holbrook, ID

The soil mapped at the center of ZIP 83243 is Iphil — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH8.2alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupBwater soaks in moderately

Farmland classNot prime farmlandUSDA classification

Map unit: Iphil-Ririe-Watercanyon complex, 8 to 20 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 83243; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Holbrook, ID

Summer high91 °Faverage high, July

Winter low15 °Faverage low, January

Hot days46days a year at 90 °F or more

Freezing nights185nights a year at 32 °F or less

Growing degree days2,221base 50 °F — the season’s usable heat

Longest day15 h 16 mindaylight on June 21

Shortest day9 h 05 mindaylight on December 21

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

Precipitation16 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: Malad City, ID (20 mi away); precipitation: Holbrook 4.0 Nne, ID (2 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

832526a

Malad City, ID · 14 mi

Snowville, UT · 26 mi

Idaho planting zones →

Questions about 83243

What planting zone is ZIP code 83243?

ZIP code 83243 (Holbrook, 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 Holbrook, ID?

The median last spring frost (32 °F) near 83243 is May 22; after June 16 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Malad City station.

When is the first frost in Holbrook, ID?

The median first fall frost near 83243 is September 20, giving a median frost-free growing season of 116 days.

When should I plant tomatoes in 83243?

Start tomato seeds indoors around Mar 27 – Apr 10 and set transplants outside around May 29 – Jun 12, one to three weeks after the median last frost.

How much rain and snow does 83243 get?

About 16 inches of precipitation a year (NOAA 1991–2020 normals, Holbrook 4.0 Nne station).

How hot do summers get in Holbrook, ID?

The average high peaks at 91 °F in July, with about 46 days a year at 90 °F or more.

What kind of soil does 83243 have?

The USDA soil survey maps Iphil at the center of ZIP 83243: silt loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Holbrook, ID in 2026?

Spring leaf-out near 83243 came on Mar 23 in 2026, 23 days earlier than the 1991–2020 average (Apr 15), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Holbrook, ID?

Long-day onions: the longest day near 83243 is 15 h 16 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 83243 change?

Yes. The 2012 USDA map put 83243 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.