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

Planting zone for 85138 — Maricopa, AZ

ZIP code 85138 (Maricopa, Pinal County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is February 23 and the first fall frost November 24.

Where ZIP 85138 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.

Zone9a20 to 25 °F

Coldest night−6.7 to −3.9 °C

Last frostFeb 23

First frostNov 24

2012 zone9a

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 9a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Maricopa, 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 Maricopa, AZ

JanFebMarAprMayJunJulAugSepOctNovDec

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

Last spring frostFebruary 23median — 50% chance of a later frost

Safe for tender plantsMarch 15only 10% chance of frost after

First fall frostNovember 24median — 10% chance by Nov 10

Growing season274 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 2 and returns around December 6.

From the NOAA station Maricopa 4 N, AZ — 7 miles away, elevation 1,161 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 85138

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Jan 12 – Jan 26

SpinachSow outdoors · Jan 12 – Feb 2

Broccoli, cabbageStart indoors · Dec 15 – Dec 29

Broccoli, cabbageTransplant · Feb 2 – Feb 16

Onion setsPlant outdoors · Jan 26 – Feb 9

PotatoesPlant outdoors · Feb 2 – Feb 16

LettuceSow outdoors · Jan 26 – Feb 9

Carrots, beetsSow outdoors · Feb 2 – Feb 16

TomatoesStart indoors · Dec 29 – Jan 12

TomatoesTransplant · Mar 2 – Mar 16

Peppers, eggplantStart indoors · Dec 15 – Dec 29

Peppers, eggplantTransplant · Mar 9 – Mar 23

BeansSow outdoors · Mar 2 – Mar 16

Sweet cornSow outdoors · Mar 2 – Mar 16

Cucumbers, squashSow outdoors · Mar 2 – Mar 16

Fall lettuce, spinachSow outdoors · Sep 29 – Oct 13

GarlicPlant cloves · Nov 10 – Dec 15

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 23) and first fall frost (Nov 24) 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 85138 came on Jan 23 — 3 days earlier than the 1991–2020 average (Jan 26).

average
Jan 262026
Jan 23

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 9a in Arizona

492 plants native to the lower 48 states, recorded in Arizona, and rated by the USDA to survive 20 °F or colder — the bottom of zone 9a. 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 Maricopa, AZ.

Soil in Maricopa, AZ

The soil mapped at the center of ZIP 85138 is Glenbar — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up

pH7.8slightly alkaline; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter0.5%low — add compost

Hydrologic groupCwater soaks in slowly

Farmland classPrime farmland if irrigated and either protected from flooding or not frequently flooded during the growing seasonUSDA classification

Map unit: Glenbar clay 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 85138; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Maricopa, AZ

Summer high109 °Faverage high, July

Winter low35 °Faverage low, December

Hot days183days a year at 90 °F or more

Freezing nights32nights a year at 32 °F or less

Growing degree days8,135base 50 °F — the season’s usable heat

Longest day14 h 20 mindaylight on June 21

Shortest day9 h 58 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation7.1 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: Maricopa 4 N, AZ (7 mi away); precipitation: Maricopa 4 N, AZ (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

Casa Grande, AZ · 16 mi

851479a

Sacaton, AZ · 16 mi

851939a

Casa Grande, AZ · 17 mi

853399b

Laveen, AZ · 18 mi

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

Questions about 85138

What planting zone is ZIP code 85138?

ZIP code 85138 (Maricopa, AZ) is in USDA hardiness zone 9a on the 2023 map: the coldest night of an average winter reaches 20 to 25 °F (−6.7 to −3.9 °C).

When is the last frost in Maricopa, AZ?

The median last spring frost (32 °F) near 85138 is February 23; after March 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Maricopa 4 N station.

When is the first frost in Maricopa, AZ?

The median first fall frost near 85138 is November 24, giving a median frost-free growing season of 274 days.

When should I plant tomatoes in 85138?

Start tomato seeds indoors around Dec 29 – Jan 12 and set transplants outside around Mar 2 – Mar 16, one to three weeks after the median last frost.

How much rain and snow does 85138 get?

About 7.1 inches of precipitation a year (NOAA 1991–2020 normals, Maricopa 4 N station).

How hot do summers get in Maricopa, AZ?

The average high peaks at 109 °F in July, with about 183 days a year at 90 °F or more.

What kind of soil does 85138 have?

The USDA soil survey maps Glenbar at the center of ZIP 85138: clay loam, well drained, pH about 7.8 (slightly alkaline).

Did spring come early in Maricopa, AZ in 2026?

Spring leaf-out near 85138 came on Jan 23 in 2026, 3 days earlier than the 1991–2020 average (Jan 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Maricopa, AZ?

Intermediate onions: the longest day near 85138 is 14 h 20 min, so day-neutral types bulb best; long-day varieties may not bulb fully.