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

Planting zone for 83728 — Boise, ID

ZIP code 83728 (Boise, Ada County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 24 and the first fall frost October 21.

Where ZIP 83728 is

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.

Zone7a0 to 5 °F
Coldest night−17.8 to −15 °C
Last frostApr 24
First frostOct 21
2012 zone7a

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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Boise, 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 Boise, ID

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 24median — 50% chance of a later frost
Safe for tender plantsMay 9only 10% chance of frost after
First fall frostOctober 21median — 10% chance by Oct 5
Growing season179 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 2 and returns around October 31.

From the NOAA station Boise Air Terminal, ID — 4 miles away, elevation 2,815 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 83728

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 13 – Mar 27
SpinachSow outdoors · Mar 13 – Apr 3
Broccoli, cabbageStart indoors · Feb 13 – Feb 27
Broccoli, cabbageTransplant · Apr 3 – Apr 17
Onion setsPlant outdoors · Mar 27 – Apr 10
PotatoesPlant outdoors · Apr 3 – Apr 17
LettuceSow outdoors · Mar 27 – Apr 10
Carrots, beetsSow outdoors · Apr 3 – Apr 17
TomatoesStart indoors · Feb 27 – Mar 13
TomatoesTransplant · May 1 – May 15
Peppers, eggplantStart indoors · Feb 13 – Feb 27
Peppers, eggplantTransplant · May 8 – May 22
BeansSow outdoors · May 1 – May 15
Sweet cornSow outdoors · May 1 – May 15
Cucumbers, squashSow outdoors · May 1 – May 15
Fall lettuce, spinachSow outdoors · Aug 26 – Sep 9
GarlicPlant cloves · Oct 7 – Nov 11
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 24) and first fall frost (Oct 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 83728 came on Mar 4 — 17 days earlier than the 1991–2020 average (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 7a in Idaho

575 plants native to the lower 48 states, recorded in Idaho, and rated by the USDA to survive 0 °F or colder — the bottom of zone 7a. Each links to its USDA PLANTS profile.

Trees 30

balsam poplar80 ft · blooms late spring · high shade tolerance · to −79 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fblue spruce100 ft · blooms late spring · medium shade tolerance · to −38 °Fboxelder60 ft · blooms early spring · low shade tolerance · to −46 °FDouglas-fir200 ft · blooms mid spring · medium shade tolerance · to −33 °FEngelmann spruce120 ft · blooms late spring · low shade tolerance · to −50 °F

Shrubs 101

alderleaf buckthorn3 ft · blooms late spring · low shade tolerance · to −33 °Falderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °Falpine laurel1 ft · blooms late spring · low shade tolerance · to −28 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °FBarclay's willow15 ft · high shade tolerance · to −43 °Fbeaked hazelnut15 ft · blooms early spring · low shade tolerance · to −47 °F

Wildflowers & perennials 277

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °Falpine bistort1 ft · blooms mid spring · high shade tolerance · to −38 °Falpine mountainsorrel1 ft · blooms mid summer · medium shade tolerance · to −43 °FAmerican alpine speedwell1 ft · blooms summer · medium shade tolerance · to −28 °FAmerican bistort1.5 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °F

Grasses 155

Alaska oniongrass3 ft · blooms mid spring · low shade tolerance · to −33 °Falkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °FAlpine Meadow-Foxtail0.5 ft · blooms mid spring · medium shade tolerance · to −33 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Fanalogue sedge1.5 ft · blooms late spring · medium shade tolerance · to −38 °F

Vines 1

western white clematis1 ft · blooms mid summer · medium shade tolerance · to −38 °F

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 Boise, ID.

Soil in Boise, ID

The center of ZIP 83728 is mapped as Urban land, 0 to 1 percent slopes: built-over ground without natural soil data. Garden soil here is usually imported or disturbed — test before you plant.

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 83728; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Boise, ID

Summer high93 °Faverage high, July
Winter low25 °Faverage low, December
Hot days55days a year at 90 °F or more
Freezing nights108nights a year at 32 °F or less
Growing degree days3,290base 50 °F — the season’s usable heat
Longest day15 h 26 mindaylight on June 21
Shortest day8 h 56 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation15.6 inper year, rain and melted snow

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 39 °F, low 26 °F 39°26° JanFebruary: average high 46 °F, low 29 °F 46°29° FebMarch: average high 56 °F, low 35 °F 56°35° MarApril: average high 62 °F, low 40 °F 62°40° AprMay: average high 72 °F, low 48 °F 72°48° MayJune: average high 81 °F, low 54 °F 81°54° JunJuly: average high 93 °F, low 62 °F 93°62° JulAugust: average high 91 °F, low 61 °F 91°61° AugSeptember: average high 80 °F, low 53 °F 80°53° SepOctober: average high 65 °F, low 42 °F 65°42° OctNovember: average high 49 °F, low 32 °F 49°32° NovDecember: average high 39 °F, low 25 °F 39°25° Dec

Precipitation by month inches

0″1″2″3″January: 1.79 in precipitation 1.8 JanFebruary: 1.34 in precipitation 1.3 FebMarch: 1.69 in precipitation 1.7 MarApril: 1.65 in precipitation 1.6 AprMay: 1.86 in precipitation 1.9 MayJune: 1.35 in precipitation 1.4 JunJuly: 0.29 in precipitation 0.3 JulAugust: 0.29 in precipitation 0.3 AugSeptember: 0.48 in precipitation 0.5 SepOctober: 0.99 in precipitation 1.0 OctNovember: 1.57 in precipitation 1.6 NovDecember: 2.31 in precipitation 2.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Boise Air Terminal, ID (4 mi away); precipitation: Boise 2.1 Nne, ID (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

837077a
Boise, ID · <1 mi
837357a
Boise, ID · <1 mi
837997a
Boise, ID · <1 mi
837207a
Boise, ID · <1 mi
837247a
Boise, ID · <1 mi
837067a
Boise, ID · 2 mi
837017a
Boise, ID · 4 mi
837037a
Boise, ID · 4 mi

All 26 ZIP codes in Boise → · Idaho planting zones →

Questions about 83728

What planting zone is ZIP code 83728?

ZIP code 83728 (Boise, ID) is in USDA hardiness zone 7a on the 2023 map: the coldest night of an average winter reaches 0 to 5 °F (−17.8 to −15 °C).

When is the last frost in Boise, ID?

The median last spring frost (32 °F) near 83728 is April 24; after May 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Boise Air Terminal station.

When is the first frost in Boise, ID?

The median first fall frost near 83728 is October 21, giving a median frost-free growing season of 179 days.

When should I plant tomatoes in 83728?

Start tomato seeds indoors around Feb 27 – Mar 13 and set transplants outside around May 1 – May 15, one to three weeks after the median last frost.

How much rain and snow does 83728 get?

About 15.6 inches of precipitation a year (NOAA 1991–2020 normals, Boise 2.1 Nne station).

How hot do summers get in Boise, ID?

The average high peaks at 93 °F in July, with about 55 days a year at 90 °F or more.

Did spring come early in Boise, ID in 2026?

Spring leaf-out near 83728 came on Mar 4 in 2026, 17 days earlier than the 1991–2020 average (Mar 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Boise, ID?

Long-day onions: the longest day near 83728 is 15 h 26 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).