San Juan County, in Utah, sits in USDA hardiness zone 7a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Well-matched crops include cabbage, pawpaw, california poppy, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
San Juan County holds more than one microclimate.
Soils and elevations shift across San Juan County, so your frost dates and drainage aren't the county average. 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 San Juan County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
San Juan County — the short answer
San Juan County, Utah: USDA zone 7a, about 176 days between hard freezes, across 5.0M acres.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 26
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 19
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~176
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 5.0M acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 7a is San Juan County's average, not your lot's — a low corner or a tree line moves it. Against San Juan County's 176-day season, see what your own ground reads.
Heat in San Juan County
Across a year, San Juan County accumulates about 2,394 growing degree days above 50°F, about 118 fewer than the middle Utah county — ahead of 12 of Utah’s 29 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in San Juan County
Across San Juan County, the ground is predominantly Entisols, where Rizno, Moenkopie, and Skos are the most extensive named soil series. The soil is generally well drained with a fine sandy loam surface. Topsoil pH runs about 7.9–8.2, moderately alkaline. Rainfall drains through hydrologic group D soils.
Soil order
Entisols
Drainage
Well drained
Prime farmland
0%
Hydric soils
1%
Soil still varies lot by lot — soil types explained.
How the ground varies across San Juan County
The USDA soil survey maps 61% of San Juan County as well drained — but another 9% drains differently: 4% somewhat excessively drained, 3% excessively drained.
Rizno is the most extensive named soil at 12% of mapped acres, then Moenkopie (5%) and Skos (4%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in San Juan County
Each reading below is measured for San Juan County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across San Juan County are well drained, in hydrologic group D — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across San Juan County runs about pH 7.9–8.2, on the alkaline side.
Many vegetables cope, but acid-lovers like blueberries struggle, and iron and manganese lock up above about pH 7.5 — leaves yellow between the veins even in rich soil.
Elemental sulfur and generous organic matter lower pH slowly for the beds that need it; test first so you add only what the soil actually calls for.
USDA NRCS SSURGO
Season length
MeasuredSan Juan County runs about 176 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSan Juan County sits in USDA hardiness zone 7a.
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 San Juan County is in
San Juan County sits in the Colorado Plateaus — EPA Level III, inside the wider North American Deserts. One consistent ecological setting across the whole county.
What Grows in San Juan County
We scored all 1,086 plants against San Juan County's own USDA zone 7a and its own 176-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Utah profile.
Is it too late to plant in San Juan County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 29; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 19 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
Documented around San Juan County
- monarch butterfly8 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in San Juan County
USGS estimates 11,974 lb of Glyphosate on San Juan County farmland in 2019, its largest by weight, ahead of Atrazine (9,878 lb) and 2,4-d (5,605 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across San Juan County — and how to grow with it.
We checked the federal record across San Juan County — 522 documented sites across 7 of the 9 source types we track.
The most significant on record: 12 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across San Juan County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near San Juan County
Closest first, across San Juan County. Listing isn't leaking, and distance isn't exposure.
- PER PROJECT BEARS EARS SITESuperfund · 4.2 mi
- KIGALIA GUARD STATIONUnderground Storage Tanks · 5.3 mi
- Peavine Queen MineMining · 5.8 mi
- Oakie MineMining · 6.3 mi
- East WoodenshoeMining · 9.0 mi
- SusieMining · 9.2 mi
- Big Red & Big Red 2Mining · 9.6 mi
- Notch # 5Mining · 9.9 mi
- Sandy No. 3 MineMining · 9.9 mi
- Sandy 3 MineMining · 10.0 mi
- Sandy No. 2 MineMining · 10.0 mi
- (D-37-18) 6bda- 1Nitrate · 10.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from San Juan County'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 San Juan County.
Sources Checked
across San Juan County
Severity Distribution
across San Juan County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around San Juan County, two things run higher than the national average across San Juan County — Mining (209 sites) and Superfund (12 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in San Juan County
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 San Juan County average
Your land is one point inside San Juan County
Everything above resolves to San Juan County as a whole — one PHZM band and one county frost record, read across 5.0M acres. 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 county 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 county average.
Your Lot vs the San Juan County Average
San Juan County Average
- ●USDA Zones 7a, averaged across San Juan County
- ●One soil character for all of San Juan County
- ●Frost dates read at San Juan County's scale: Apr 26 to Oct 19
YOUR Parcel
- ✓Your exact zone, not San Juan County's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in San Juan County
Pull a site-specific report for your exact address in San Juan County, Utah — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that San Juan County averages can't show:
We read public map data around San Juan County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the San Juan County average
How we know this about San Juan County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where San Juan County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about San Juan County
When does frost risk typically end in San Juan County?
The last hard freeze (28°F) in San Juan County typically lands around Apr 26, 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 May 17.
How long is the growing season in San Juan County?
Measured between 28°F hard freezes, San Juan County sees about 176 frost-free days — roughly Apr 26 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 17 to Oct 5, about 141 days.
Is the soil safe to grow vegetables in San Juan County?
The federal record around San Juan County is a meaningful one — 522 documented sites, mostly Mining entries (209), the nearest Superfund record about 4.2 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.
Everything above is measured at San Juan County's scale — its 7a band and its 176-day season. Your yard writes its own version of San Juan County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Utah's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at San Juan County’s own scale
9 of the readings below were taken at San Juan County's own scale — its own ~176-day span between 28°F freezes, the 3 most extensive soil series mapped here and 522 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- San Juan County's own USDA hardiness band, zones 7aUSDA PHZM 2023
- San Juan County's own 28°F hard-freeze dates and its ~176-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in San Juan CountyUSDA NRCS SSURGO
- 522 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Superfund record about 4.2 miles outFederal environmental registers
- San Juan County's boundary and the 5,007,155 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~176-day seasonGrowable Ground crop-matching engine
- San Juan County sitting wholly inside the Colorado PlateausUS EPA Level III Ecoregions
- Open occurrence records documented in San Juan County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto San Juan County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Utah grower plans around — written at state scale, so they stay on the state guidefrom Utah
What this page can’t tell you
- How the season shifts across San Juan County — the ~176 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among San Juan County's 5,007,155 acreswhy one lot differs from the next →
- Which of those 522 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over San Juan Countyread your own land →