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

Planting zone for 83217 — Bancroft, ID

ZIP code 83217 (Bancroft, Caribou County) is in USDA zone 5a: the coldest winter night averages −20 to −15 °F. The median last spring frost is May 21 and the first fall frost September 21.

Where ZIP 83217 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.

Zone5a−20 to −15 °F

Coldest night−28.9 to −26.1 °C

Last frostMay 21

First frostSep 21

2012 zone5a

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 5a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Bancroft, 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 Bancroft, ID

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMay 21median — 50% chance of a later frost

Safe for tender plantsJune 11only 10% chance of frost after

First fall frostSeptember 21median — 10% chance by Sep 3

Growing season118 daysfrost-free, median

A hard freeze (28 °F) usually ends around May 3 and returns around October 5.

From the NOAA station Lava Hot Springs, ID — 11 miles away, elevation 4,597 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 83217

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 9 – Apr 23

SpinachSow outdoors · Apr 9 – Apr 30

Broccoli, cabbageStart indoors · Mar 12 – Mar 26

Broccoli, cabbageTransplant · Apr 30 – May 14

Onion setsPlant outdoors · Apr 23 – May 7

PotatoesPlant outdoors · Apr 30 – May 14

LettuceSow outdoors · Apr 23 – May 7

Carrots, beetsSow outdoors · Apr 30 – May 14

TomatoesStart indoors · Mar 26 – Apr 9

TomatoesTransplant · May 28 – Jun 11

Peppers, eggplantStart indoors · Mar 12 – Mar 26

Peppers, eggplantTransplant · Jun 4 – Jun 18

BeansSow outdoors · May 28 – Jun 11

Sweet cornSow outdoors · May 28 – Jun 11

Cucumbers, squashSow outdoors · May 28 – Jun 11

Fall lettuce, spinachSow outdoors · Jul 27 – Aug 10

GarlicPlant cloves · Sep 7 – Oct 12

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 21) and first fall frost (Sep 21) 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 83217 came on Apr 1 — 20 days earlier than the 1991–2020 average (Apr 21).

average
Apr 212026
Apr 1

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 5a in Idaho

536 plants native to the lower 48 states, recorded in Idaho, and rated by the USDA to survive −20 °F or colder — the bottom of zone 5a. 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 Bancroft, ID.

Soil in Bancroft, ID

The soil mapped at the center of ZIP 83217 is Ririe — silt loam, well drained.

TextureSilt loama good balance for most vegetables

pH7.6slightly alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter3%moderate

Hydrologic groupCwater soaks in slowly

Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Ririe-Rexburg complex, deep, 1 to 4 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 83217; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Bancroft, ID

Summer high87 °Faverage high, July

Winter low14 °Faverage low, January

Hot days28days a year at 90 °F or more

Freezing nights178nights a year at 32 °F or less

Growing degree days1,912base 50 °F — the season’s usable heat

Longest day15 h 20 mindaylight on June 21

Shortest day9 h 02 mindaylight on December 21

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

Precipitation18.3 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: Lava Hot Springs, ID (11 mi away); precipitation: Lava Hot Springs, ID (11 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

832466b

Lava Hot Springs, ID · 12 mi

Pocatello, ID · 25 mi

832056a

Pocatello, ID · 25 mi

832765a

Soda Springs, ID · 25 mi

832146b

Arimo, ID · 25 mi

Idaho planting zones →

Questions about 83217

What planting zone is ZIP code 83217?

ZIP code 83217 (Bancroft, ID) is in USDA hardiness zone 5a on the 2023 map: the coldest night of an average winter reaches −20 to −15 °F (−28.9 to −26.1 °C).

When is the last frost in Bancroft, ID?

The median last spring frost (32 °F) near 83217 is May 21; after June 11 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Lava Hot Springs station.

When is the first frost in Bancroft, ID?

The median first fall frost near 83217 is September 21, giving a median frost-free growing season of 118 days.

When should I plant tomatoes in 83217?

Start tomato seeds indoors around Mar 26 – Apr 9 and set transplants outside around May 28 – Jun 11, one to three weeks after the median last frost.

How much rain and snow does 83217 get?

About 18.3 inches of precipitation a year (NOAA 1991–2020 normals, Lava Hot Springs station).

How hot do summers get in Bancroft, ID?

The average high peaks at 87 °F in July, with about 28 days a year at 90 °F or more.

What kind of soil does 83217 have?

The USDA soil survey maps Ririe at the center of ZIP 83217: silt loam, well drained, pH about 7.6 (slightly alkaline).

Did spring come early in Bancroft, ID in 2026?

Spring leaf-out near 83217 came on Apr 1 in 2026, 20 days earlier than the 1991–2020 average (Apr 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Bancroft, ID?

Long-day onions: the longest day near 83217 is 15 h 20 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).