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

Planting zone for 85643 — Willcox, AZ

ZIP code 85643 (Willcox, Cochise County) is in USDA zone 8b: the coldest winter night averages 15 to 20 °F. The median last spring frost is April 9 and the first fall frost October 31.

Where ZIP 85643 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.

Zone8b15 to 20 °F
Coldest night−9.4 to −6.7 °C
Last frostApr 9
First frostOct 31
2012 zone8a

Was 8a 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 8b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Willcox, AZ…

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 Willcox, AZ

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 9median — 50% chance of a later frost
Safe for tender plantsApril 29only 10% chance of frost after
First fall frostOctober 31median — 10% chance by Oct 20
Growing season204 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 16 and returns around November 12.

From the NOAA station Willcox, AZ — 17 miles away, elevation 4,170 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 85643

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Feb 26 – Mar 12
SpinachSow outdoors · Feb 26 – Mar 19
Broccoli, cabbageStart indoors · Jan 29 – Feb 12
Broccoli, cabbageTransplant · Mar 19 – Apr 2
Onion setsPlant outdoors · Mar 12 – Mar 26
PotatoesPlant outdoors · Mar 19 – Apr 2
LettuceSow outdoors · Mar 12 – Mar 26
Carrots, beetsSow outdoors · Mar 19 – Apr 2
TomatoesStart indoors · Feb 12 – Feb 26
TomatoesTransplant · Apr 16 – Apr 30
Peppers, eggplantStart indoors · Jan 29 – Feb 12
Peppers, eggplantTransplant · Apr 23 – May 7
BeansSow outdoors · Apr 16 – Apr 30
Sweet cornSow outdoors · Apr 16 – Apr 30
Cucumbers, squashSow outdoors · Apr 16 – Apr 30
Fall lettuce, spinachSow outdoors · Sep 5 – Sep 19
GarlicPlant cloves · Oct 17 – Nov 21
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 9) and first fall frost (Oct 31) 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 85643 came on Feb 5 — about the same time as the 1991–2020 average (Feb 4).

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 8b in Arizona

482 plants native to the lower 48 states, recorded in Arizona, and rated by the USDA to survive 15 °F or colder — the bottom of zone 8b. Each links to its USDA PLANTS profile.

Trees 25

Arizona cypress50 ft · blooms spring · low shade tolerance · to −23 °FArizona madrone30 ft · blooms late spring · high shade tolerance · to −4 °FArizona sycamore80 ft · blooms early spring · high shade tolerance · to −8 °FArizona walnut50 ft · blooms late spring · high shade tolerance · to −33 °Fblack locust60 ft · blooms spring · high shade tolerance · to −37 °Fblue spruce100 ft · blooms late spring · medium shade tolerance · to −38 °F

Shrubs 105

alderleaf mountain mahogany15 ft · blooms late spring · medium shade tolerance · to −41 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °FAmerican tarwort3 ft · blooms late spring · high shade tolerance · to −23 °Fantelope bitterbrush6 ft · blooms early spring · medium shade tolerance · to −36 °FApache plume6 ft · blooms late spring · high shade tolerance · to −23 °Fbig sagebrush4 ft · blooms mid summer · high shade tolerance · to −43 °F

Wildflowers & perennials 196

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 century plant6 ft · blooms indeterminate · high shade tolerance · to 12 °F

Grasses 147

alkali cordgrass3 ft · blooms late summer · high shade tolerance · to −38 °Falkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °Falpine timothy1.4 ft · blooms late spring · medium shade tolerance · to −43 °Fanalogue sedge1.5 ft · blooms late spring · medium shade tolerance · to −38 °FArizona cottontop4 ft · blooms late summer · high shade tolerance · to −13 °FArizona fescue2 ft · blooms late spring · high shade tolerance · to −23 °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 Willcox, AZ.

Soil in Willcox, AZ

The soil mapped at the center of ZIP 85643 is Sonoita — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupAwater soaks in fast
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Sonoita sandy loam, 0 to 2 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 85643; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Willcox, AZ

Summer high97 °Faverage high, June
Winter low28 °Faverage low, January
Hot days119days a year at 90 °F or more
Freezing nights93nights a year at 32 °F or less
Growing degree days5,044base 50 °F — the season’s usable heat
Longest day14 h 17 mindaylight on June 21
Shortest day10 h 01 mindaylight on December 21
Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb
Precipitation12.4 inper year, rain and melted snow
Snowfall2 inper year

Average high and low, by month

20°30°40°50°60°70°80°90°100°110°32 °FJanuary: average high 61 °F, low 28 °F 61°28° JanFebruary: average high 65 °F, low 32 °F 65°32° FebMarch: average high 72 °F, low 36 °F 72°36° MarApril: average high 79 °F, low 42 °F 79°42° AprMay: average high 87 °F, low 50 °F 87°50° MayJune: average high 97 °F, low 59 °F 97°59° JunJuly: average high 96 °F, low 66 °F 96°66° JulAugust: average high 94 °F, low 65 °F 94°65° AugSeptember: average high 90 °F, low 57 °F 90°57° SepOctober: average high 82 °F, low 45 °F 82°45° OctNovember: average high 71 °F, low 34 °F 71°34° NovDecember: average high 60 °F, low 28 °F 60°28° Dec

Precipitation by month inches · ❄ = snowfall

0″1″2″3″January: 1.02 in precipitation, 0.6 in snowfall 1.0❄1 JanFebruary: 0.93 in precipitation, 0.6 in snowfall 0.9❄1 FebMarch: 0.66 in precipitation, 0.1 in snowfall 0.7 MarApril: 0.22 in precipitation 0.2 AprMay: 0.34 in precipitation 0.3 MayJune: 0.45 in precipitation 0.5 JunJuly: 2.62 in precipitation 2.6 JulAugust: 2.48 in precipitation 2.5 AugSeptember: 1.21 in precipitation 1.2 SepOctober: 0.68 in precipitation 0.7 OctNovember: 0.70 in precipitation, 0.2 in snowfall 0.7 NovDecember: 1.09 in precipitation, 0.2 in snowfall 1.1 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Willcox, AZ (17 mi away); precipitation: Willcox, AZ (17 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

856448a
Willcox, AZ · 17 mi
855488b
Safford, AZ · 27 mi
856098b
Dragoon, AZ · 28 mi
855528b
Thatcher, AZ · 28 mi
855468b
Safford, AZ · 29 mi
855318b
Central, AZ · 31 mi
856028b
Benson, AZ · 31 mi
856068b
Cochise, AZ · 32 mi

All 2 ZIP codes in Willcox → · Arizona planting zones →

Questions about 85643

What planting zone is ZIP code 85643?

ZIP code 85643 (Willcox, AZ) is in USDA hardiness zone 8b on the 2023 map: the coldest night of an average winter reaches 15 to 20 °F (−9.4 to −6.7 °C).

When is the last frost in Willcox, AZ?

The median last spring frost (32 °F) near 85643 is April 9; after April 29 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Willcox station.

When is the first frost in Willcox, AZ?

The median first fall frost near 85643 is October 31, giving a median frost-free growing season of 204 days.

When should I plant tomatoes in 85643?

Start tomato seeds indoors around Feb 12 – Feb 26 and set transplants outside around Apr 16 – Apr 30, one to three weeks after the median last frost.

How much rain and snow does 85643 get?

About 12.4 inches of precipitation a year and 2 inches of snowfall (NOAA 1991–2020 normals, Willcox station).

How hot do summers get in Willcox, AZ?

The average high peaks at 97 °F in June, with about 119 days a year at 90 °F or more.

What kind of soil does 85643 have?

The USDA soil survey maps Sonoita at the center of ZIP 85643: sandy loam, well drained, pH about 6.7 (neutral).

Did spring come early in Willcox, AZ in 2026?

Spring leaf-out near 85643 came on Feb 5 in 2026, about the same as the 1991–2020 average (Feb 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Willcox, AZ?

Short-day onions: the longest day near 85643 is 14 h 17 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.

Did the zone for 85643 change?

Yes. The 2012 USDA map put 85643 in zone 8a; the 2023 map puts it in zone 8b. The newer map uses 1991–2020 data and more weather stations.