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

Planting zone for 85637 — Sonoita, AZ

ZIP code 85637 (Sonoita, Santa Cruz County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is March 28 and the first fall frost November 21.

Where ZIP 85637 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.

Zone8a10 to 15 °F

Coldest night−12.2 to −9.4 °C

Last frostMar 28

First frostNov 21

2012 zone8a

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 8a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Sonoita, 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 Sonoita, AZ

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostMarch 28median — 50% chance of a later frost

Safe for tender plantsApril 21only 10% chance of frost after

First fall frostNovember 21median — 10% chance by Nov 5

Growing season237 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 1 and returns around December 2.

From the NOAA station Sonoita, AZ — 3 miles away, elevation 4,895 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 85637

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 14 – Feb 28

SpinachSow outdoors · Feb 14 – Mar 7

Broccoli, cabbageStart indoors · Jan 17 – Jan 31

Broccoli, cabbageTransplant · Mar 7 – Mar 21

Onion setsPlant outdoors · Feb 28 – Mar 14

PotatoesPlant outdoors · Mar 7 – Mar 21

LettuceSow outdoors · Feb 28 – Mar 14

Carrots, beetsSow outdoors · Mar 7 – Mar 21

TomatoesStart indoors · Jan 31 – Feb 14

TomatoesTransplant · Apr 4 – Apr 18

Peppers, eggplantStart indoors · Jan 17 – Jan 31

Peppers, eggplantTransplant · Apr 11 – Apr 25

BeansSow outdoors · Apr 4 – Apr 18

Sweet cornSow outdoors · Apr 4 – Apr 18

Cucumbers, squashSow outdoors · Apr 4 – Apr 18

Fall lettuce, spinachSow outdoors · Sep 26 – Oct 10

GarlicPlant cloves · Nov 7 – Dec 12

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 28) and first fall frost (Nov 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 85637 came on Jan 31 — 4 days earlier than the 1991–2020 average (Feb 4).

average
Feb 42026
Jan 31

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 8a in Arizona

472 plants native to the lower 48 states, recorded in Arizona, and rated by the USDA to survive 10 °F or colder — the bottom of zone 8a. 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 Sonoita, AZ.

Soil in Sonoita, AZ

The soil mapped at the center of ZIP 85637 is White House — gravelly loam, well drained.

TextureGravelly loama good balance for most vegetables

pH6.1slightly acidic; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter1.5%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classNot prime farmlandUSDA classification

Map unit: White House gravelly loam, 10 to 35 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 85637; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Sonoita, AZ

Summer high91 °Faverage high, June

Winter low33 °Faverage low, January

Hot days60days a year at 90 °F or more

Freezing nights41nights a year at 32 °F or less

Growing degree days4,761base 50 °F — the season’s usable heat

Longest day14 h 13 mindaylight on June 21

Shortest day10 h 04 mindaylight on December 21

Onions to growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb

Precipitation20.6 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: Sonoita, AZ (3 mi away); precipitation: Santa Rita Exp Range, AZ (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

856118a

Elgin, AZ · 12 mi

856248a

Patagonia, AZ · 14 mi

856149a

Green Valley, AZ · 15 mi

856288b

Nogales, AZ · 18 mi

856138b

Fort Huachuca, AZ · 21 mi

856168b

Huachuca City, AZ · 22 mi

856368b

Sierra Vista, AZ · 24 mi

856718b

Sierra Vista, AZ · 25 mi

Arizona planting zones →

Questions about 85637

What planting zone is ZIP code 85637?

ZIP code 85637 (Sonoita, AZ) is in USDA hardiness zone 8a on the 2023 map: the coldest night of an average winter reaches 10 to 15 °F (−12.2 to −9.4 °C).

When is the last frost in Sonoita, AZ?

The median last spring frost (32 °F) near 85637 is March 28; after April 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Sonoita station.

When is the first frost in Sonoita, AZ?

The median first fall frost near 85637 is November 21, giving a median frost-free growing season of 237 days.

When should I plant tomatoes in 85637?

Start tomato seeds indoors around Jan 31 – Feb 14 and set transplants outside around Apr 4 – Apr 18, one to three weeks after the median last frost.

How much rain and snow does 85637 get?

About 20.6 inches of precipitation a year (NOAA 1991–2020 normals, Santa Rita Exp Range station).

How hot do summers get in Sonoita, AZ?

The average high peaks at 91 °F in June, with about 60 days a year at 90 °F or more.

What kind of soil does 85637 have?

The USDA soil survey maps White House at the center of ZIP 85637: gravelly loam, well drained, pH about 6.1 (slightly acidic).

Did spring come early in Sonoita, AZ in 2026?

Spring leaf-out near 85637 came on Jan 31 in 2026, 4 days earlier than the 1991–2020 average (Feb 4), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Sonoita, AZ?

Short-day onions: the longest day near 85637 is 14 h 13 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.