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

Planting zone for 85350 — Somerton, AZ

ZIP code 85350 (Somerton, Yuma County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.

Where ZIP 85350 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.

Zone10a30 to 35 °F

Coldest night−1.1 to 1.7 °C

Last frostrare

First frostrare

2012 zone10a

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 10a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Somerton, 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

A 32 °F frost doesn't happen here in most winters. At the nearest station (NOAA station Yuma Quartermaster Depot, AZ — 12 miles away, elevation 161 ft) the median growing season is 362 days. When frost does come, it is a midwinter night or two; cover tender plants when a freeze is forecast.

Frost data: NOAA NCEI U.S. Climate Normals 1991–2020.

When spring arrived in 2026

In 2026, spring leaf-out near 85350 came on Jan 19 — about the same time as the 1991–2020 average (Jan 21).

average
Jan 212026
Jan 19

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 10a in Arizona

506 plants native to the lower 48 states, recorded in Arizona, and rated by the USDA to survive 30 °F or colder — the bottom of zone 10a. 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 Somerton, AZ.

Soil in Somerton, AZ

The soil mapped at the center of ZIP 85350 is Gadsden — clay, well drained.

TextureClayholds water and nutrients; slow to drain and warm up

pH8.2alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter0.75%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classPrime farmland if irrigated and reclaimed of excess salts and sodiumUSDA classification

Map unit: Gadsden clay.

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 85350; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Somerton, AZ

Summer high107 °Faverage high, July

Winter low47 °Faverage low, December

Hot days181days a year at 90 °F or more

Freezing nights0nights a year at 32 °F or less

Growing degree days9,509base 50 °F — the season’s usable heat

Longest day14 h 18 mindaylight on June 21

Shortest day10 h 00 mindaylight on December 21

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

Precipitation3.3 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: Yuma Mcas, AZ (8 mi away); precipitation: Yuma Mcas, AZ (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 10a.

Winterhaven, CA · 23 mi

Arizona planting zones →

Questions about 85350

What planting zone is ZIP code 85350?

ZIP code 85350 (Somerton, AZ) is in USDA hardiness zone 10a on the 2023 map: the coldest night of an average winter reaches 30 to 35 °F (−1.1 to 1.7 °C).

How much rain and snow does 85350 get?

About 3.3 inches of precipitation a year (NOAA 1991–2020 normals, Yuma Mcas station).

How hot do summers get in Somerton, AZ?

The average high peaks at 107 °F in July, with about 181 days a year at 90 °F or more.

What kind of soil does 85350 have?

The USDA soil survey maps Gadsden at the center of ZIP 85350: clay, well drained, pH about 8.2 (alkaline).

Did spring come early in Somerton, AZ in 2026?

Spring leaf-out near 85350 came on Jan 19 in 2026, about the same as the 1991–2020 average (Jan 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Somerton, AZ?

Short-day onions: the longest day near 85350 is 14 h 18 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.