Circle City, Arizona, sits in USDA hardiness zone 9b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
These conditions suit okra, meyer lemon, california poppy, and artichoke — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Even in Circle City, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Circle City lot. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Circle City — soil, climate, flood, and parcel records. How we handle your address.
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Circle City — the short answer
Circle City, Arizona: USDA zone 9b, about 345 days between hard freezes, across 195 acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 15
- Maricopa County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 26
- Maricopa County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~345
- Maricopa County normal — NOAA 1991–2020, nearest to this town
- Town area
- 195 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. No 30-year normal resolves at this town’s own centroid, so the hard-freeze dates are Maricopa County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Circle City's average, not your lot's — a low corner or a tree line moves it. Against Circle City's 345-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Circle City
Each reading below is measured for Circle City itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsCircle City runs about 345 days between hard freezes (read from Maricopa County, the closest normal to Circle City) — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredCircle City sits in USDA hardiness zone 9b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Circle City is in
Circle City sits in the Sonoran Basin and Range — EPA Level III, inside the wider North American Deserts. That is read at Circle City's own centroid rather than borrowed from Maricopa County.
What Grows in Circle City
Every plant below cleared Circle City's own zone 9b and its 345-day season. Each card opens that plant's Arizona profile. How we score.
Is it too late to plant in Circle City?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Jan 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jan 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 26 — long-season crops need about 90 days of runway, quick greens only 30. And with a calendar this mild, the honest answer is that planting barely stops — winter opens seasons colder regions never see.
Documented around Circle City
Survey cells within 31 miles of Circle City checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 269 miles off. What to watch for.
What's on the federal record near Circle City
Closest first, within ~10 miles of Circle City. Listing isn't leaking, and distance isn't exposure.
- B-06-03 33DCBNitrate · 1800 ft
- DESERT OASIS RV PARKUnderground Storage Tanks · 2500 ft
- PARCEL #503-16-011Underground Storage Tanks · 1.7 mi
- B-05-03 15AAANitrate · 2.8 mi
- BRANDYS AUTOBrownfields · 2.8 mi
- WELLS QUICK STOPUnderground Storage Tanks · 3.6 mi
- WICKENBURG VULTURE MERCURY DROPPINGS SITESuperfund · 3.6 mi
- B-06-03 36DDDNitrate · 3.6 mi
- MORRISTOWN ELEMENTARY SCHOOLUnderground Storage Tanks · 3.6 mi
- MORRISTOWN TRANSFER STATION WTCSBrownfields · 3.7 mi
- DOLLAR GENERALUnderground Storage Tanks · 3.7 mi
- 503-22-013Underground Storage Tanks · 3.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Circle City's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Circle City.
Total Sites
78
within ~10 miles of Circle City
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Circle City
Severity Distribution
within ~10 miles of Circle City
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Circle City, two things run higher than the national average within ~10 miles of Circle City — Mining (37 sites) and Nitrate (22 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Circle City
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Circle City average
Your land is one point inside Circle City
Everything above resolves to Circle City as a whole — one PHZM band, read across 195 acres, with hard-freeze dates borrowed from Maricopa County’s record because no 30-year normal resolves at this town’s own centroid. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at town scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better local average.
Your Lot vs the Circle City Average
Circle City Average
- ●USDA Zones 9b, averaged across Circle City
- ●One soil character for all of Circle City
- ●Frost dates read at Circle City's scale: Jan 15 to Dec 26
YOUR Parcel
- ✓Your exact zone, not Circle City's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Circle City
Pull a site-specific report for your exact address in Circle City, Arizona — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Circle City averages can't show:
We read public map data around Circle City — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Circle City average
How we know this about Circle City
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Maricopa County’s record, because none resolves here; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Circle City
When does frost risk typically end in Circle City?
The last hard freeze (28°F) in Circle City typically lands around Jan 15, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Feb 5.
When is the first frost in Circle City?
The first hard freeze (28°F) in Circle City typically arrives around Dec 26, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Dec 12, so the watching starts about Nov 26 — about 345 days after the spring freeze cleared.
How long is the growing season in Circle City?
Measured between 28°F hard freezes, Circle City sees about 345 frost-free days — roughly Jan 15 through Dec 26, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 5 to Dec 12, about 310 days.
Is the soil safe to grow vegetables in Circle City?
The federal record around Circle City is a meaningful one — 78 documented sites, mostly Mining entries (37), the nearest Nitrate record about 0.3 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do I protect my plants from frost in Circle City?
From about Nov 26 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Dec 26 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Dec 26. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Circle City's scale — its 9b band and its 345-day season. Your yard writes its own version of Circle City's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Circle City’s own scale
6 of the readings below were taken at Circle City's own scale — the 195 acres it covers and 78 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Circle City's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 78 documented contamination sites on the federal record near Circle City, the closest Nitrate record about 0.3 miles out from the town centreFederal environmental registers
- Circle City's boundary and the 195 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~345-day seasonGrowable Ground crop-matching engine
- The ecoregion at Circle City's own centroid, the Sonoran Basin and RangeUS EPA Level III Ecoregions
- Lanternfly survey cells around Circle City checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- The 28°F hard-freeze dates — Circle City has no normal of its own, so its county's is the closest measured readfrom Maricopa County
- Soil character — no town-scale survey exists, so Circle City's 195 acres read through its county's SSURGO summaryfrom Maricopa County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Maricopa County
- The growing challenges every Arizona grower plans around — written at state scale, so they stay on the state guidefrom Arizona
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Maricopa County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Circle City's 195 acreswhy one lot differs from the next →
- Which side of Circle City you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 195 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.3 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Circle City-wide figureread your own land →