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

Planting zone for 85140 — San Tan Valley, AZ

ZIP code 85140 (San Tan Valley, Pinal County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is February 1 and the first fall frost December 11.

Where ZIP 85140 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.

Zone9b25 to 30 °F
Coldest night−3.9 to −1.1 °C
Last frostFeb 1
First frostDec 11
2012 zone9b

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 9b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for San Tan Valley, 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 San Tan Valley, AZ

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostFebruary 1median — 50% chance of a later frost
Safe for tender plantsFebruary 27only 10% chance of frost after
First fall frostDecember 11median — 10% chance by Nov 23
Growing season315 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 8 and returns around December 26.

From the NOAA station Chandler Heights, AZ — 12 miles away, elevation 1,424 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 85140

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Dec 21 – Jan 4
SpinachSow outdoors · Dec 21 – Jan 11
Broccoli, cabbageStart indoors · Nov 23 – Dec 7
Broccoli, cabbageTransplant · Jan 11 – Jan 25
Onion setsPlant outdoors · Jan 4 – Jan 18
PotatoesPlant outdoors · Jan 11 – Jan 25
LettuceSow outdoors · Jan 4 – Jan 18
Carrots, beetsSow outdoors · Jan 11 – Jan 25
TomatoesStart indoors · Dec 7 – Dec 21
TomatoesTransplant · Feb 8 – Feb 22
Peppers, eggplantStart indoors · Nov 23 – Dec 7
Peppers, eggplantTransplant · Feb 15 – Mar 1
BeansSow outdoors · Feb 8 – Feb 22
Sweet cornSow outdoors · Feb 8 – Feb 22
Cucumbers, squashSow outdoors · Feb 8 – Feb 22
Fall lettuce, spinachSow outdoors · Oct 16 – Oct 30
GarlicPlant cloves · Nov 27 – Jan 1
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 1) and first fall frost (Dec 11) 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 85140 came on Jan 21 — 3 days earlier than the 1991–2020 average (Jan 24).

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 9b in Arizona

499 plants native to the lower 48 states, recorded in Arizona, and rated by the USDA to survive 25 °F or colder — the bottom of zone 9b. 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 113

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 199

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 152

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 San Tan Valley, AZ.

Soil in San Tan Valley, AZ

The soil mapped at the center of ZIP 85140 is Denure — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH7.9alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupAwater soaks in fast
Farmland classNot prime farmlandUSDA classification

Map unit: Denure-Mohall complex, 1 to 5 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 85140; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in San Tan Valley, AZ

Summer high104 °Faverage high, July
Winter low39 °Faverage low, December
Hot days165days a year at 90 °F or more
Freezing nights11nights a year at 32 °F or less
Growing degree days7,921base 50 °F — the season’s usable heat
Longest day14 h 21 mindaylight on June 21
Shortest day9 h 57 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation9.4 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°110°32 °FJanuary: average high 66 °F, low 41 °F 66°41° JanFebruary: average high 70 °F, low 43 °F 70°43° FebMarch: average high 77 °F, low 48 °F 77°48° MarApril: average high 85 °F, low 53 °F 85°53° AprMay: average high 93 °F, low 62 °F 93°62° MayJune: average high 103 °F, low 71 °F 103°71° JunJuly: average high 104 °F, low 79 °F 104°79° JulAugust: average high 103 °F, low 78 °F 103°78° AugSeptember: average high 98 °F, low 72 °F 98°72° SepOctober: average high 87 °F, low 59 °F 87°59° OctNovember: average high 74 °F, low 47 °F 74°47° NovDecember: average high 64 °F, low 39 °F 64°39° Dec

Precipitation by month inches

0″1″2″January: 1.20 in precipitation 1.2 JanFebruary: 1.19 in precipitation 1.2 FebMarch: 0.95 in precipitation 0.9 MarApril: 0.28 in precipitation 0.3 AprMay: 0.20 in precipitation 0.2 MayJune: 0.12 in precipitation 0.1 JunJuly: 0.91 in precipitation 0.9 JulAugust: 1.53 in precipitation 1.5 AugSeptember: 0.83 in precipitation 0.8 SepOctober: 0.52 in precipitation 0.5 OctNovember: 0.83 in precipitation 0.8 NovDecember: 0.80 in precipitation 0.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Chandler Heights, AZ (12 mi away); precipitation: Queen Creek 3.9 Ene, AZ (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9b.

851439b
San Tan Valley, AZ · 7 mi
852129b
Mesa, AZ · 10 mi
851199b
Apache Junction, AZ · 10 mi
851209b
Apache Junction, AZ · 10 mi
851189b
Gold Canyon, AZ · 10 mi
851179b
Apache Junction, AZ · 11 mi
851429b
Queen Creek, AZ · 11 mi
851789b
Apache Junction, AZ · 11 mi

All 2 ZIP codes in San Tan Valley → · Arizona planting zones →

Questions about 85140

What planting zone is ZIP code 85140?

ZIP code 85140 (San Tan Valley, AZ) is in USDA hardiness zone 9b on the 2023 map: the coldest night of an average winter reaches 25 to 30 °F (−3.9 to −1.1 °C).

When is the last frost in San Tan Valley, AZ?

The median last spring frost (32 °F) near 85140 is February 1; after February 27 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Chandler Heights station.

When is the first frost in San Tan Valley, AZ?

The median first fall frost near 85140 is December 11, giving a median frost-free growing season of 315 days.

When should I plant tomatoes in 85140?

Start tomato seeds indoors around Dec 7 – Dec 21 and set transplants outside around Feb 8 – Feb 22, one to three weeks after the median last frost.

How much rain and snow does 85140 get?

About 9.4 inches of precipitation a year (NOAA 1991–2020 normals, Queen Creek 3.9 Ene station).

How hot do summers get in San Tan Valley, AZ?

The average high peaks at 104 °F in July, with about 165 days a year at 90 °F or more.

What kind of soil does 85140 have?

The USDA soil survey maps Denure at the center of ZIP 85140: sandy loam, well drained, pH about 7.9 (alkaline).

Did spring come early in San Tan Valley, AZ in 2026?

Spring leaf-out near 85140 came on Jan 21 in 2026, 3 days earlier than the 1991–2020 average (Jan 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in San Tan Valley, AZ?

Intermediate onions: the longest day near 85140 is 14 h 21 min, so day-neutral types bulb best; long-day varieties may not bulb fully.