Spencer, Idaho, sits in USDA hardiness zone 5a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Well-matched crops include cabbage, cranberry, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Spencer, 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 Spencer 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 Spencer — soil, climate, flood, and parcel records. How we handle your address.
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Spencer — the short answer
Spencer, Idaho: USDA zone 5a, about 141 days between hard freezes, across 731 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)
- Oct 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~141
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 731 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 Spencer's average, not your lot's — a low corner or a tree line moves it. Against Spencer's 141-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Spencer
Each reading below is measured for Spencer itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSpencer runs about 141 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
MeasuredSpencer 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 Spencer is in
Spencer sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Spencer's own centroid rather than borrowed from Clark County.
What Grows in Spencer
Every plant below cleared Spencer's own zone 5a and its 141-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Spencer?
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 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 Oct 3 — long-season crops need about 90 days of runway, quick greens only 30. In a season this compact, fast finishers and cold-hardy greens do the late work, and garlic tucked in before the freeze repays you next summer.
What's on the federal record near Spencer
Closest first, within ~10 miles of Spencer. Listing isn't leaking, and distance isn't exposure.
- SPENCER BAR & GRILLUnderground Storage Tanks · 2600 ft
- AT&T Communications Spencer ""J""Underground Storage Tanks · 2600 ft
- SPENCER SECTIONUnderground Storage Tanks · 2600 ft
- EUGENE R HUNTERUnderground Storage Tanks · 0.6 mi
- 12N 36E 24CCB1Nitrate · 1.5 mi
- Lone Pine GroupMining · 3.0 mi
- 13N 36E 34BBA1 STODDARD CREEK CAMPGROUNDNitrate · 3.6 mi
- 11N 37E 09ACA1Nitrate · 6.3 mi
- Viola MineMining · 8.1 mi
- 11N 36E 34AAC1Nitrate · 8.6 mi
- USDA ARS ID DUBOIS SHEEP EXPERIMENT STATIONSuperfund · 8.7 mi
- USDA ARS ID DUBOIS SHEEP EXPERIMENT STATIONBrownfields · 8.7 mi
Measured from Spencer'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 Spencer.
Total Sites
16
within ~10 miles of Spencer
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Spencer
Severity Distribution
within ~10 miles of Spencer
Highest-Severity Sites
Know Before You Grow
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Mine waste leaches heavy metals. Test for lead, arsenic and cadmium before growing food here.
Check your specific parcel in Spencer
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 Spencer average
Your land is one point inside Spencer
Everything above resolves to Spencer as a whole — one PHZM band and one 28°F frost record, read across 731 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 Spencer Average
Spencer Average
- ●USDA Zones 5a, averaged across Spencer
- ●One soil character for all of Spencer
- ●Frost dates read at Spencer's scale: May 15 to Oct 3
YOUR Parcel
- ✓Your exact zone, not Spencer's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Spencer
Pull a site-specific report for your exact address in Spencer, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Spencer averages can't show:
We read public map data around Spencer — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Spencer average
How we know this about Spencer
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 Spencer’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 Spencer
When does frost risk typically end in Spencer?
The last hard freeze (28°F) in Spencer 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 Spencer?
The first hard freeze (28°F) in Spencer typically arrives around Oct 3, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 19, so the watching starts about Sep 3 — about 141 days after the spring freeze cleared.
How long is the growing season in Spencer?
Measured between 28°F hard freezes, Spencer sees about 141 frost-free days — roughly May 15 through Oct 3, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 5 to Sep 19, about 106 days.
Is the soil safe to grow vegetables in Spencer?
The federal record around Spencer is a meaningful one — 16 documented sites, mostly Nitrate entries (8), the nearest Underground Storage Tanks 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 Spencer?
With about 141 frost-free days between hard freezes, Spencer 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 169 to 197 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 Spencer's scale — its 5a band and its 141-day season. Your yard writes its own version of Spencer'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 Spencer’s own scale
6 of the readings below were taken at Spencer's own scale — its own ~141-day season between 28°F freezes, the 731 acres it covers and 16 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Spencer's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Spencer's own 28°F hard-freeze dates, about May 15 and Oct 3 and the ~141-day span between themNOAA 1991–2020 Climate Normals
- 16 documented contamination sites on the federal record near Spencer, the closest Underground Storage Tanks record about 0.5 miles out from the town centreFederal environmental registers
- Spencer's boundary and the 731 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~141-day seasonGrowable Ground crop-matching engine
- The ecoregion at Spencer's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Spencer's 731 acres read through its county's SSURGO summaryfrom Clark County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Clark 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 Clark County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Spencer's 731 acreswhy one lot differs from the next →
- Which side of Spencer you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 731 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 Spencer-wide figureread your own land →