Roberts, 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.
Growers here do well with cabbage, cranberry, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Roberts, 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 Roberts 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 Roberts — soil, climate, flood, and parcel records. How we handle your address.
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Roberts — the short answer
Roberts, Idaho: USDA zone 5a, about 145 days between hard freezes, across 201 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 9
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 1
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~145
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 201 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 Roberts's average, not your lot's — a low corner or a tree line moves it. Against Roberts's 145-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Roberts
Each reading below is measured for Roberts itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredRoberts runs about 145 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
MeasuredRoberts 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 Roberts is in
Roberts sits in the Snake River Plain — EPA Level III, inside the wider North American Deserts. That is read at Roberts's own centroid rather than borrowed from Jefferson County.
What Grows in Roberts
Every plant below cleared Roberts's own zone 5a and its 145-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Roberts?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Apr 11; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 9 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 1 — 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 Roberts
Closest first, within ~10 miles of Roberts. Listing isn't leaking, and distance isn't exposure.
- CLARK'S LUMBER CO., INC.Underground Storage Tanks · 250 ft
- ROBERTS STATIONUnderground Storage Tanks · 350 ft
- 05N 37E 32DDB1Nitrate · 1600 ft
- 05N 37E 32ADA1Nitrate · 1800 ft
- ROBERTS BUS MAINTENANCE GARAGEUnderground Storage Tanks · 2300 ft
- 05N 37E 33BDC1Nitrate · 0.6 mi
- ERNEST J BARNESUnderground Storage Tanks · 0.8 mi
- 05N 37E 21CCC1Nitrate · 1.6 mi
- 04N 36E 01DDB1Nitrate · 2.3 mi
- 04N 36E 02CDA1Nitrate · 3.4 mi
- GOLDEN VALLEY PACKERS INCUnderground Storage Tanks · 3.6 mi
- 05N 37E 08CCC1Nitrate · 3.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Roberts'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 Roberts.
Total Sites
104
within ~10 miles of Roberts
Risk Level
Moderate
Highest-severity
3 concentrated animal feeding operations
Sources Checked
within ~10 miles of Roberts
Severity Distribution
within ~10 miles of Roberts
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Roberts, two things run higher than the national average within ~10 miles of Roberts — CAFO (3 sites) and Nitrate (80 sites). That's not a problem with your land — it's information about it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Roberts
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 Roberts average
Your land is one point inside Roberts
Everything above resolves to Roberts as a whole — one PHZM band and one 28°F frost record, read across 201 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 Roberts Average
Roberts Average
- ●USDA Zones 5a, averaged across Roberts
- ●One soil character for all of Roberts
- ●Frost dates read at Roberts's scale: May 9 to Oct 1
YOUR Parcel
- ✓Your exact zone, not Roberts's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Roberts
Pull a site-specific report for your exact address in Roberts, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Roberts averages can't show:
We read public map data around Roberts — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Roberts average
How we know this about Roberts
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 Roberts’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 Roberts
When does frost risk typically end in Roberts?
The last hard freeze (28°F) in Roberts typically lands around May 9, 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 30.
When is the first frost in Roberts?
The first hard freeze (28°F) in Roberts typically arrives around Oct 1, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 17, so the watching starts about Sep 1 — about 145 days after the spring freeze cleared.
How long is the growing season in Roberts?
Measured between 28°F hard freezes, Roberts sees about 145 frost-free days — roughly May 9 through Oct 1, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 30 to Sep 17, about 110 days.
Is the soil safe to grow vegetables in Roberts?
The federal record around Roberts shows 104 documented sites, mostly Nitrate entries (80), the nearest Underground Storage Tanks record under a tenth of a mile out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do gardeners stretch the season in Roberts?
With about 145 frost-free days between hard freezes, Roberts 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 173 to 201 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 9 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Roberts's scale — its 5a band and its 145-day season. Your yard writes its own version of Roberts'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 Roberts’s own scale
6 of the readings below were taken at Roberts's own scale — its own ~145-day season between 28°F freezes, the 201 acres it covers and 104 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Roberts's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Roberts's own 28°F hard-freeze dates, about May 9 and Oct 1 and the ~145-day span between themNOAA 1991–2020 Climate Normals
- 104 documented contamination sites on the federal record near Roberts, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Roberts's boundary and the 201 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~145-day seasonGrowable Ground crop-matching engine
- The ecoregion at Roberts's own centroid, the Snake River PlainUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Roberts's 201 acres read through its county's SSURGO summaryfrom Jefferson County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Jefferson 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 Jefferson County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Roberts's 201 acreswhy one lot differs from the next →
- Which side of Roberts you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 201 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record under a tenth of a mile 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 Roberts-wide figureread your own land →