Warm River, Idaho, sits in USDA hardiness zone 5a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
These conditions suit cabbage, cranberry, lavender, and collard greens — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Even in Warm River, 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 Warm River 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 Warm River — soil, climate, flood, and parcel records. How we handle your address.
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Warm River — the short answer
Warm River, Idaho: USDA zone 5a, about 132 days between hard freezes, across 426 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 15
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 24
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~132
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 426 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 5a is Warm River's average, not your lot's — a low corner or a tree line moves it. Against Warm River's 132-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Warm River
Each reading below is measured for Warm River itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredWarm River runs about 132 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredWarm River sits in USDA hardiness zone 5a.
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 Warm River is in
Warm River sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Warm River's own centroid rather than borrowed from Fremont County.
What Grows in Warm River
Every plant below cleared Warm River's own zone 5a and its 132-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Warm River?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Apr 17; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 24 — long-season crops need about 90 days of runway, quick greens only 30. When the window is tight, the fall moves are quick ones — baby greens, radishes, and garlic set for next season.
What's on the federal record near Warm River
Closest first, within ~10 miles of Warm River. Listing isn't leaking, and distance isn't exposure.
- 09N 43E 13ABB1Nitrate · 0.5 mi
- 09N 43E 14ADA1Nitrate · 1.1 mi
- UNION PACIFIC RAILROAD (7)Underground Storage Tanks · 1.2 mi
- 09N 43E 14DDC1Nitrate · 1.6 mi
- 09N 43E 23AAB1Nitrate · 1.8 mi
- 09N 44E 08BDA1Nitrate · 1.8 mi
- 09N 44E 17ABC1Nitrate · 2.0 mi
- 09N 43E 25AAA1Nitrate · 2.5 mi
- 09N 43E 25AAA2Nitrate · 2.6 mi
- 09N 44E 30CBB1Nitrate · 3.0 mi
- 09N 43E 16DAB1Nitrate · 3.1 mi
- C&M FARMS INCUnderground Storage Tanks · 3.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Warm River'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 Warm River.
Total Sites
231
within ~10 miles of Warm River
Risk Level
Elevated
Highest-severity
206 nitrate monitoring sites
Severity Distribution
within ~10 miles of Warm River
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Warm River, Nitrate runs higher than the national average — 206 sites within ~10 miles of Warm River. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Warm River
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 Warm River average
Your land is one point inside Warm River
Everything above resolves to Warm River as a whole — one PHZM band and one 28°F frost record, read across 426 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 city 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 Warm River Average
Warm River Average
- ●USDA Zones 5a, averaged across Warm River
- ●One soil character for all of Warm River
- ●Frost dates read at Warm River's scale: May 15 to Sep 24
YOUR Parcel
- ✓Your exact zone, not Warm River's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Warm River
Pull a site-specific report for your exact address in Warm River, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Warm River averages can't show:
We read public map data around Warm River — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Warm River average
How we know this about Warm River
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Warm River’s own record; 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 city grain anywhere on this page — there is no city-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 Warm River
When does frost risk typically end in Warm River?
The last hard freeze (28°F) in Warm River typically lands around May 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 Jun 5.
When is the first frost in Warm River?
The first hard freeze (28°F) in Warm River typically arrives around Sep 24, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 10, so the watching starts about Aug 25 — about 132 days after the spring freeze cleared.
How long is the growing season in Warm River?
Measured between 28°F hard freezes, Warm River sees about 132 frost-free days — roughly May 15 through Sep 24, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 5 to Sep 10, about 97 days.
Is the soil safe to grow vegetables in Warm River?
The federal record around Warm River is a meaningful one — 231 documented sites, mostly Nitrate entries (206), the nearest Nitrate record about 0.5 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 gardeners stretch the season in Warm River?
With about 132 frost-free days between hard freezes, Warm River rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 160 to 188 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 15 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Warm River's scale — its 5a band and its 132-day season. Your yard writes its own version of Warm River'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 Warm River’s own scale
6 of the readings below were taken at Warm River's own scale — its own ~132-day season between 28°F freezes, the 426 acres it covers and 231 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Warm River's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Warm River's own 28°F hard-freeze dates, about May 15 and Sep 24 and the ~132-day span between themNOAA 1991–2020 Climate Normals
- 231 documented contamination sites on the federal record near Warm River, the closest Nitrate record about 0.5 miles out from the town centreFederal environmental registers
- Warm River's boundary and the 426 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~132-day seasonGrowable Ground crop-matching engine
- The ecoregion at Warm River's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Warm River's 426 acres read through its county's SSURGO summaryfrom Fremont County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Fremont County
- The growing challenges every Idaho grower plans around — written at state scale, so they stay on the state guidefrom Idaho
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Fremont County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Warm River's 426 acreswhy one lot differs from the next →
- Which side of Warm River you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 426 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.5 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 Warm River-wide figureread your own land →
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