Rio Arriba County, in New Mexico, sits in USDA hardiness zone 6a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Growers here do well with cabbage, blackberry, california poppy, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Rio Arriba County lies within the Northern New Mexico / Española Valley — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Rio Arriba County holds more than one microclimate.
Soils and elevations shift across Rio Arriba 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 Rio Arriba County — soil, climate, flood, and parcel records. How we handle your address.
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Rio Arriba County — the short answer
Rio Arriba County, New Mexico: USDA zone 6a, about 159 days between hard freezes, across 3.8M acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 4
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 10
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~159
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 3.8M 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 6a is Rio Arriba County's average, not your lot's — a low corner or a tree line moves it. Against Rio Arriba County's 159-day season, see what your own ground reads.
One county, several growing seasons
Rio Arriba County's hard-freeze record runs about 159 days between freezes — but that is the county-wide average, and several towns inside it carry a markedly different season in their own 30-year record: Brazos at about 126 days, Ensenada at 126, Los Ojos at 126 and Tierra Amarilla at 126 (against the county's ~159).
Those are measured records, not estimates. If you garden in one of these pockets, plant against your own town's season rather than the county's ~159-day average.
NOAA Regional Climate Centers ACIS (1991–2020), 30-year daily minimum record. Only held-out towns carrying their own record are named — a town with no record of its own is absent rather than estimated, and a county with nothing qualifying shows no spread at all.
Heat in Rio Arriba County
Across a year, Rio Arriba County accumulates about 1,729 growing degree days above 50°F, about 1,444 fewer than the middle New Mexico county — ahead of 2 of New Mexico’s 33 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 Rio Arriba County
Across Rio Arriba County, the ground is predominantly Alfisols, where Orlie, Vessilla, and Menefee are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 6.8–7.8, neutral. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Well drained
Hydric soils
2%
Soil still varies lot by lot — soil types explained.
How the ground varies across Rio Arriba County
The USDA soil survey maps 94% of Rio Arriba County as well drained — but another 4% drains differently: 1% somewhat poorly drained, 1% excessively drained.
Orlie is the most extensive named soil at 7% of mapped acres, then Vessilla (7%) and Menefee (6%).
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 Rio Arriba County
Each reading below is measured for Rio Arriba 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 Rio Arriba County are well drained, in hydrologic group C — 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 Rio Arriba County runs about pH 6.8–7.8, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredRio Arriba County runs about 159 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
MeasuredRio Arriba County sits in USDA hardiness zone 6a.
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 Rio Arriba County is in
Rio Arriba County spans 3 EPA Level III ecoregions — Southern Rockies (73%), Arizona/New Mexico Plateau (21%) and Colorado Plateaus (6%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Rio Arriba County
We scored all 1,086 plants against Rio Arriba County's own USDA zone 6a and its own 159-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 New Mexico profile.
Is it too late to plant in Rio Arriba County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Apr 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 10 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Documented around Rio Arriba County
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Rio Arriba County
USGS estimates 3,032 lb of Dicamba on Rio Arriba County farmland in 2019, its largest by weight, ahead of Glyphosate (2,188 lb) and Triclopyr (1,100 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 Rio Arriba County — and how to grow with it.
We checked the federal record across Rio Arriba County — 464 documented sites across 6 of the 9 source types we track.
The most significant on record: 4 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Rio Arriba County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Rio Arriba County
Closest first, across Rio Arriba County. Listing isn't leaking, and distance isn't exposure.
- EL VADO LAKE RV PARKUnderground Storage Tanks · 6.0 mi
- EL VADO DAMUnderground Storage Tanks · 10.7 mi
- BRUTSCHE PILARUnderground Storage Tanks · 11.7 mi
- 25N.01E.17.234Nitrate · 11.8 mi
- EL CUERNO LLC AND CONVENIENT STOREUnderground Storage Tanks · 11.8 mi
- EL VADO RANCH INCUnderground Storage Tanks · 13.4 mi
- TIERRA AMARILLA ARMY RADAR STATIONUnderground Storage Tanks · 13.4 mi
- EL VADO LAKE STATE PARKUnderground Storage Tanks · 13.4 mi
- CHAMA VALLEY SCHOOLSUnderground Storage Tanks · 13.4 mi
- 27N.04E.13.411ANitrate · 13.6 mi
- HERON LAKE STOREUnderground Storage Tanks · 13.9 mi
- OLD KOA KAMPGROUND .Underground Storage Tanks · 14.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Rio Arriba 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 Rio Arriba County.
Sources Checked
across Rio Arriba County
Severity Distribution
across Rio Arriba County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Rio Arriba County, two things run higher than the national average across Rio Arriba County — Mining (151 sites) and Nitrate (120 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 Rio Arriba 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 Rio Arriba County average
Your land is one point inside Rio Arriba County
Everything above resolves to Rio Arriba County as a whole — one PHZM band and one county frost record, read across 3.8M 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 Rio Arriba County Average
Rio Arriba County Average
- ●USDA Zones 6a, averaged across Rio Arriba County
- ●One soil character for all of Rio Arriba County
- ●Frost dates read at Rio Arriba County's scale: May 4 to Oct 10
YOUR Parcel
- ✓Your exact zone, not Rio Arriba County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Rio Arriba County
Pull a site-specific report for your exact address in Rio Arriba County, New Mexico — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Rio Arriba County averages can't show:
We read public map data around Rio Arriba County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Rio Arriba County average
How we know this about Rio Arriba 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 Rio Arriba County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Rio Arriba County
When does frost risk typically end in Rio Arriba County?
The last hard freeze (28°F) in Rio Arriba County typically lands around May 4, 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 25.
How long is the growing season in Rio Arriba County?
Measured between 28°F hard freezes, Rio Arriba County sees about 159 frost-free days — roughly May 4 through Oct 10, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 25 to Sep 26, about 124 days.
Is the soil safe to grow vegetables in Rio Arriba County?
The federal record around Rio Arriba County runs heavier than most — 464 documented sites, mostly Mining entries (151), the nearest Underground Storage Tanks record about 6.0 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
Everything above is measured at Rio Arriba County's scale — its 6a band and its 159-day season. Your yard writes its own version of Rio Arriba 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 New Mexico's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Rio Arriba County’s own scale
9 of the readings below were taken at Rio Arriba County's own scale — its own ~159-day span between 28°F freezes, the 3 most extensive soil series mapped here and 464 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Rio Arriba County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Rio Arriba County's own 28°F hard-freeze dates and its ~159-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Rio Arriba CountyUSDA NRCS SSURGO
- 464 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 6.0 miles outFederal environmental registers
- Rio Arriba County's boundary and the 3,750,957 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~159-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions Rio Arriba County spans, Southern Rockies the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Rio Arriba County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Rio Arriba County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every New Mexico grower plans around — written at state scale, so they stay on the state guidefrom New Mexico
What this page can’t tell you
- How the season shifts across Rio Arriba County — the ~159 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 Rio Arriba County's 3,750,957 acreswhy one lot differs from the next →
- Which of those 464 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 Rio Arriba Countyread your own land →