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

Planting zone for 85128 — Coolidge, AZ

ZIP code 85128 (Coolidge, Pinal County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is February 17 and the first fall frost November 29.

Where ZIP 85128 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 17
First frostNov 29
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 Coolidge, 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 Coolidge, AZ

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostFebruary 17median — 50% chance of a later frost
Safe for tender plantsMarch 8only 10% chance of frost after
First fall frostNovember 29median — 10% chance by Nov 12
Growing season284 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 26 and returns around December 12.

From the NOAA station Casa Grande Nm, AZ — 2 miles away, elevation 1,421 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 85128

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 6 – Jan 20
SpinachSow outdoors · Jan 6 – Jan 27
Broccoli, cabbageStart indoors · Dec 9 – Dec 23
Broccoli, cabbageTransplant · Jan 27 – Feb 10
Onion setsPlant outdoors · Jan 20 – Feb 3
PotatoesPlant outdoors · Jan 27 – Feb 10
LettuceSow outdoors · Jan 20 – Feb 3
Carrots, beetsSow outdoors · Jan 27 – Feb 10
TomatoesStart indoors · Dec 23 – Jan 6
TomatoesTransplant · Feb 24 – Mar 10
Peppers, eggplantStart indoors · Dec 9 – Dec 23
Peppers, eggplantTransplant · Mar 3 – Mar 17
BeansSow outdoors · Feb 24 – Mar 10
Sweet cornSow outdoors · Feb 24 – Mar 10
Cucumbers, squashSow outdoors · Feb 24 – Mar 10
Fall lettuce, spinachSow outdoors · Oct 4 – Oct 18
GarlicPlant cloves · Nov 15 – Dec 20
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 17) and first fall frost (Nov 29) 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 85128 came on Jan 26 — about the same time as the 1991–2020 average (Jan 26).

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.

Trees 26

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 109

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 197

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 151

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 Coolidge, AZ.

Soil in Coolidge, AZ

The soil mapped at the center of ZIP 85128 is Mohall — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
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 irrigatedUSDA classification

Map unit: Mohall sandy 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 85128; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Coolidge, AZ

Summer high107 °Faverage high, July
Winter low36 °Faverage low, December
Hot days180days a year at 90 °F or more
Freezing nights29nights a year at 32 °F or less
Growing degree days7,927base 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
Precipitation8.3 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°110°120°32 °FJanuary: average high 68 °F, low 37 °F 68°37° JanFebruary: average high 71 °F, low 40 °F 71°40° FebMarch: average high 78 °F, low 45 °F 78°45° MarApril: average high 86 °F, low 51 °F 86°51° AprMay: average high 95 °F, low 59 °F 95°59° MayJune: average high 105 °F, low 68 °F 105°68° JunJuly: average high 107 °F, low 77 °F 107°77° JulAugust: average high 105 °F, low 77 °F 105°77° AugSeptember: average high 101 °F, low 70 °F 101°70° SepOctober: average high 91 °F, low 56 °F 91°56° OctNovember: average high 78 °F, low 44 °F 78°44° NovDecember: average high 67 °F, low 36 °F 67°36° Dec

Precipitation by month inches

0″1″2″January: 0.98 in precipitation 1.0 JanFebruary: 1.02 in precipitation 1.0 FebMarch: 0.94 in precipitation 0.9 MarApril: 0.25 in precipitation 0.3 AprMay: 0.20 in precipitation 0.2 MayJune: 0.06 in precipitation 0.1 JunJuly: 1.12 in precipitation 1.1 JulAugust: 1.24 in precipitation 1.2 AugSeptember: 0.70 in precipitation 0.7 SepOctober: 0.48 in precipitation 0.5 OctNovember: 0.49 in precipitation 0.5 NovDecember: 0.77 in precipitation 0.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Casa Grande Nm, AZ (2 mi away); precipitation: Casa Grande Nm, AZ (2 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.

851919a
Valley Farms, AZ · 4 mi
851949a
Casa Grande, AZ · 8 mi
851439b
San Tan Valley, AZ · 13 mi
851229a
Casa Grande, AZ · 14 mi
851309a
Casa Grande, AZ · 15 mi
851479a
Sacaton, AZ · 16 mi
851429b
Queen Creek, AZ · 18 mi
851409b
San Tan Valley, AZ · 20 mi

Arizona planting zones →

Questions about 85128

What planting zone is ZIP code 85128?

ZIP code 85128 (Coolidge, 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 Coolidge, AZ?

The median last spring frost (32 °F) near 85128 is February 17; after March 8 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Casa Grande Nm station.

When is the first frost in Coolidge, AZ?

The median first fall frost near 85128 is November 29, giving a median frost-free growing season of 284 days.

When should I plant tomatoes in 85128?

Start tomato seeds indoors around Dec 23 – Jan 6 and set transplants outside around Feb 24 – Mar 10, one to three weeks after the median last frost.

How much rain and snow does 85128 get?

About 8.3 inches of precipitation a year (NOAA 1991–2020 normals, Casa Grande Nm station).

How hot do summers get in Coolidge, AZ?

The average high peaks at 107 °F in July, with about 180 days a year at 90 °F or more.

What kind of soil does 85128 have?

The USDA soil survey maps Mohall at the center of ZIP 85128: sandy loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Coolidge, AZ in 2026?

Spring leaf-out near 85128 came on Jan 26 in 2026, about the same as the 1991–2020 average (Jan 26), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Coolidge, AZ?

Intermediate onions: the longest day near 85128 is 14 h 20 min, so day-neutral types bulb best; long-day varieties may not bulb fully.