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

Planting zone for 85122 — Casa Grande, AZ

ZIP code 85122 (Casa Grande, Pinal County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F. The median last spring frost is February 5 and the first fall frost December 6.

Where ZIP 85122 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 5
First frostDec 6
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 Casa Grande, 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 Casa Grande, AZ

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostFebruary 5median — 50% chance of a later frost
Safe for tender plantsFebruary 28only 10% chance of frost after
First fall frostDecember 6median — 10% chance by Nov 18
Growing season305 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 14 and returns around December 22.

From the NOAA station Casa Grande, AZ — 2 miles away, elevation 1,401 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 85122

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Dec 25 – Jan 8
SpinachSow outdoors · Dec 25 – Jan 15
Broccoli, cabbageStart indoors · Nov 27 – Dec 11
Broccoli, cabbageTransplant · Jan 15 – Jan 29
Onion setsPlant outdoors · Jan 8 – Jan 22
PotatoesPlant outdoors · Jan 15 – Jan 29
LettuceSow outdoors · Jan 8 – Jan 22
Carrots, beetsSow outdoors · Jan 15 – Jan 29
TomatoesStart indoors · Dec 11 – Dec 25
TomatoesTransplant · Feb 12 – Feb 26
Peppers, eggplantStart indoors · Nov 27 – Dec 11
Peppers, eggplantTransplant · Feb 19 – Mar 5
BeansSow outdoors · Feb 12 – Feb 26
Sweet cornSow outdoors · Feb 12 – Feb 26
Cucumbers, squashSow outdoors · Feb 12 – Feb 26
Fall lettuce, spinachSow outdoors · Oct 11 – Oct 25
GarlicPlant cloves · Nov 22 – Dec 27
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 5) and first fall frost (Dec 6) 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 85122 came on Jan 24 — 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 Casa Grande, AZ.

Soil in Casa Grande, AZ

The soil mapped at the center of ZIP 85122 is Ginland — 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 matter1.25%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: Ginland 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 85122; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Casa Grande, AZ

Summer high107 °Faverage high, July
Winter low38 °Faverage low, December
Hot days184days a year at 90 °F or more
Freezing nights17nights a year at 32 °F or less
Growing degree days8,266base 50 °F — the season’s usable heat
Longest day14 h 19 mindaylight on June 21
Shortest day9 h 59 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation7.9 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 69 °F, low 39 °F 69°39° JanFebruary: average high 73 °F, low 42 °F 73°42° FebMarch: average high 80 °F, low 47 °F 80°47° MarApril: average high 88 °F, low 53 °F 88°53° AprMay: average high 96 °F, low 60 °F 96°60° MayJune: average high 106 °F, low 70 °F 106°70° JunJuly: average high 107 °F, low 78 °F 107°78° JulAugust: average high 105 °F, low 77 °F 105°77° AugSeptember: average high 100 °F, low 71 °F 100°71° SepOctober: average high 91 °F, low 57 °F 91°57° OctNovember: average high 78 °F, low 45 °F 78°45° NovDecember: average high 68 °F, low 38 °F 68°38° Dec

Precipitation by month inches

0″1″2″January: 0.79 in precipitation 0.8 JanFebruary: 1.00 in precipitation 1.0 FebMarch: 0.76 in precipitation 0.8 MarApril: 0.21 in precipitation 0.2 AprMay: 0.18 in precipitation 0.2 MayJune: 0.18 in precipitation 0.2 JunJuly: 0.91 in precipitation 0.9 JulAugust: 1.52 in precipitation 1.5 AugSeptember: 0.72 in precipitation 0.7 SepOctober: 0.48 in precipitation 0.5 OctNovember: 0.43 in precipitation 0.4 NovDecember: 0.73 in precipitation 0.7 Dec

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

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9a.

851949a
Casa Grande, AZ · 7 mi
851309a
Casa Grande, AZ · 7 mi
851939a
Casa Grande, AZ · 9 mi
851729a
Stanfield, AZ · 12 mi
851479a
Sacaton, AZ · 13 mi
851289a
Coolidge, AZ · 14 mi
851239a
Arizona City, AZ · 15 mi
851389a
Maricopa, AZ · 16 mi

All 4 ZIP codes in Casa Grande → · Arizona planting zones →

Questions about 85122

What planting zone is ZIP code 85122?

ZIP code 85122 (Casa Grande, 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 Casa Grande, AZ?

The median last spring frost (32 °F) near 85122 is February 5; after February 28 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Casa Grande station.

When is the first frost in Casa Grande, AZ?

The median first fall frost near 85122 is December 6, giving a median frost-free growing season of 305 days.

When should I plant tomatoes in 85122?

Start tomato seeds indoors around Dec 11 – Dec 25 and set transplants outside around Feb 12 – Feb 26, one to three weeks after the median last frost.

How much rain and snow does 85122 get?

About 7.9 inches of precipitation a year (NOAA 1991–2020 normals, Casa Grande station).

How hot do summers get in Casa Grande, AZ?

The average high peaks at 107 °F in July, with about 184 days a year at 90 °F or more.

What kind of soil does 85122 have?

The USDA soil survey maps Ginland at the center of ZIP 85122: clay, well drained, pH about 8.2 (alkaline).

Did spring come early in Casa Grande, AZ in 2026?

Spring leaf-out near 85122 came on Jan 24 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 Casa Grande, AZ?

Intermediate onions: the longest day near 85122 is 14 h 19 min, so day-neutral types bulb best; long-day varieties may not bulb fully.