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

Planting zone for 83606 — Caldwell, ID

ZIP code 83606 (Caldwell, Canyon County) is in USDA zone 7a: the coldest winter night averages 0 to 5 °F. The median last spring frost is April 27 and the first fall frost October 9.

Where ZIP 83606 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 27
First frostOct 9
2012 zone6b

Was 6b 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 7a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Caldwell, 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 Caldwell, ID

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 27median — 50% chance of a later frost
Safe for tender plantsMay 9only 10% chance of frost after
First fall frostOctober 9median — 10% chance by Sep 26
Growing season165 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 12 and returns around October 22.

From the NOAA station Parma Exp Stn, ID — 9 miles away, elevation 2,290 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 83606

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 16 – Mar 30
SpinachSow outdoors · Mar 16 – Apr 6
Broccoli, cabbageStart indoors · Feb 16 – Mar 2
Broccoli, cabbageTransplant · Apr 6 – Apr 20
Onion setsPlant outdoors · Mar 30 – Apr 13
PotatoesPlant outdoors · Apr 6 – Apr 20
LettuceSow outdoors · Mar 30 – Apr 13
Carrots, beetsSow outdoors · Apr 6 – Apr 20
TomatoesStart indoors · Mar 2 – Mar 16
TomatoesTransplant · May 4 – May 18
Peppers, eggplantStart indoors · Feb 16 – Mar 2
Peppers, eggplantTransplant · May 11 – May 25
BeansSow outdoors · May 4 – May 18
Sweet cornSow outdoors · May 4 – May 18
Cucumbers, squashSow outdoors · May 4 – May 18
Fall lettuce, spinachSow outdoors · Aug 14 – Aug 28
GarlicPlant cloves · Sep 25 – Oct 30
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 27) and first fall frost (Oct 9) 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 83606 came on Mar 10 — 10 days earlier than the 1991–2020 average (Mar 20).

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 Caldwell, ID.

Soil in Caldwell, ID

The soil mapped at the center of ZIP 83606 is Jenness — loam, well drained.

TextureLoama good balance for most vegetables
pH7.2neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Jenness loam, 0 to 1 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 83606; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Caldwell, ID

Summer high92 °Faverage high, July
Winter low23 °Faverage low, January
Hot days58days a year at 90 °F or more
Freezing nights144nights a year at 32 °F or less
Growing degree days2,912base 50 °F — the season’s usable heat
Longest day15 h 27 mindaylight on June 21
Shortest day8 h 55 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation10 inper year, rain and melted snow
Snowfall12 inper year

Average high and low, by month

10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 37 °F, low 23 °F 37°23° JanFebruary: average high 46 °F, low 26 °F 46°26° FebMarch: average high 57 °F, low 31 °F 57°31° MarApril: average high 64 °F, low 36 °F 64°36° AprMay: average high 73 °F, low 46 °F 73°46° MayJune: average high 81 °F, low 52 °F 81°52° JunJuly: average high 92 °F, low 57 °F 92°57° JulAugust: average high 91 °F, low 55 °F 91°55° AugSeptember: average high 82 °F, low 46 °F 82°46° SepOctober: average high 66 °F, low 36 °F 66°36° OctNovember: average high 49 °F, low 28 °F 49°28° NovDecember: average high 38 °F, low 23 °F 38°23° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″January: 1.33 in precipitation, 3.3 in snowfall 1.3❄3 JanFebruary: 0.81 in precipitation, 1.8 in snowfall 0.8❄2 FebMarch: 0.88 in precipitation, 0.4 in snowfall 0.9 MarApril: 0.89 in precipitation 0.9 AprMay: 1.37 in precipitation 1.4 MayJune: 0.78 in precipitation 0.8 JunJuly: 0.25 in precipitation 0.3 JulAugust: 0.19 in precipitation 0.2 AugSeptember: 0.64 in precipitation 0.6 SepOctober: 0.73 in precipitation 0.7 OctNovember: 0.99 in precipitation, 1.2 in snowfall 1.0❄1 NovDecember: 1.12 in precipitation, 4.8 in snowfall 1.1❄5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Parma Exp Stn, ID (9 mi away); precipitation: Parma Exp Stn, ID (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7a.

836567a
Notus, ID · <1 mi
836077a
Caldwell, ID · 3 mi
836267a
Greenleaf, ID · 4 mi
836767a
Wilder, ID · 7 mi
836607a
Parma, ID · 8 mi
836307a
Huston, ID · 8 mi
836057a
Caldwell, ID · 8 mi
836527a
Nampa, ID · 9 mi

All 3 ZIP codes in Caldwell → · Idaho planting zones →

Questions about 83606

What planting zone is ZIP code 83606?

ZIP code 83606 (Caldwell, 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 Caldwell, ID?

The median last spring frost (32 °F) near 83606 is April 27; after May 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Parma Exp Stn station.

When is the first frost in Caldwell, ID?

The median first fall frost near 83606 is October 9, giving a median frost-free growing season of 165 days.

When should I plant tomatoes in 83606?

Start tomato seeds indoors around Mar 2 – Mar 16 and set transplants outside around May 4 – May 18, one to three weeks after the median last frost.

How much rain and snow does 83606 get?

About 10 inches of precipitation a year and 12 inches of snowfall (NOAA 1991–2020 normals, Parma Exp Stn station).

How hot do summers get in Caldwell, ID?

The average high peaks at 92 °F in July, with about 58 days a year at 90 °F or more.

What kind of soil does 83606 have?

The USDA soil survey maps Jenness at the center of ZIP 83606: loam, well drained, pH about 7.2 (neutral).

Did spring come early in Caldwell, ID in 2026?

Spring leaf-out near 83606 came on Mar 10 in 2026, 10 days earlier than the 1991–2020 average (Mar 20), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Caldwell, ID?

Long-day onions: the longest day near 83606 is 15 h 27 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 83606 change?

Yes. The 2012 USDA map put 83606 in zone 6b; the 2023 map puts it in zone 7a. The newer map uses 1991–2020 data and more weather stations.