Sumas, Washington, sits in USDA hardiness zone 8a — a zone band wide enough that plant choice, not possibility, is the interesting question.
These conditions suit cabbage, fig, california poppy, and collard greens — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Even in Sumas, 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 Sumas 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 Sumas — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Sumas — the short answer
Sumas, Washington: USDA zone 8a, about 268 days between hard freezes, across 939 acres of city.
- USDA zone
- 8a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 27
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 22
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~268
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 939 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 8a is Sumas's average, not your lot's — a low corner or a tree line moves it. Against Sumas's 268-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Sumas
Each reading below is measured for Sumas itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSumas runs about 268 days between hard freezes — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSumas sits in USDA hardiness zone 8a.
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 Sumas is in
Sumas sits in the Puget Lowland — EPA Level III, inside the wider Marine West Coast Forest. That is read at Sumas's own centroid, and it is not what its county reads: Whatcom County is mostly North Cascades. The wider page above you is answering a different question about different ground.
What Grows in Sumas
Every plant below cleared Sumas's own zone 8a and its 268-day season. Each card opens that plant's Washington profile. How we score.
Is it too late to plant in Sumas?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Jan 30; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 27 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 22 — long-season crops need about 90 days of runway, quick greens only 30. And with a calendar this mild, the honest answer is that planting barely stops — winter opens seasons colder regions never see.
What's on the federal record near Sumas
Closest first, within ~10 miles of Sumas. Listing isn't leaking, and distance isn't exposure.
- CHERRY STREET MARKETUnderground Storage Tanks · 850 ft
- SUMAS SHELLUnderground Storage Tanks · 950 ft
- SUMAS GAS N SHOP INCUnderground Storage Tanks · 950 ft
- PAY N RUN 2 SUPER DUPERUnderground Storage Tanks · 1000 ft
- SUMAS TANK N TOTEUnderground Storage Tanks · 1300 ft
- YORKYS GROCERYUnderground Storage Tanks · 1300 ft
- SUPER SAVE MINI MART LLCUnderground Storage Tanks · 1500 ft
- SUMAS CENTRAL OFFICE 6678-434Underground Storage Tanks · 1600 ft
- MT BAKER FUEL COMPANY INCUnderground Storage Tanks · 1800 ft
- SOCCO INCToxics Release Inventory · 2200 ft
- USA #68407Underground Storage Tanks · 2200 ft
- SUMAS GENERATING FACILITYBrownfields · 2200 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Sumas'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 Sumas.
Sources Checked
within ~10 miles of Sumas
Severity Distribution
within ~10 miles of Sumas
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Sumas, two things run higher than the national average within ~10 miles of Sumas — CAFO (60 sites) and Nitrate (300 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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 Sumas
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 Sumas average
Your land is one point inside Sumas
Everything above resolves to Sumas as a whole — one PHZM band and one 28°F frost record, read across 939 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 Sumas Average
Sumas Average
- ●USDA Zones 8a, averaged across Sumas
- ●One soil character for all of Sumas
- ●Frost dates read at Sumas's scale: Feb 27 to Nov 22
YOUR Parcel
- ✓Your exact zone, not Sumas's 8a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Sumas
Pull a site-specific report for your exact address in Sumas, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Sumas averages can't show:
We read public map data around Sumas — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Sumas average
How we know this about Sumas
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 Sumas’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 Sumas
When does frost risk typically end in Sumas?
The last hard freeze (28°F) in Sumas typically lands around Feb 27, 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 Mar 20.
When is the first frost in Sumas?
The first hard freeze (28°F) in Sumas typically arrives around Nov 22, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 8, so the watching starts about Oct 23 — about 268 days after the spring freeze cleared.
How long is the growing season in Sumas?
Measured between 28°F hard freezes, Sumas sees about 268 frost-free days — roughly Feb 27 through Nov 22, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 20 to Nov 8, about 233 days.
Is the soil safe to grow vegetables in Sumas?
The federal record around Sumas is a meaningful one — 462 documented sites, mostly Nitrate entries (300), the nearest Underground Storage Tanks record about 0.2 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.
How do I protect my plants from frost in Sumas?
From about Oct 23 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Nov 22 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Nov 22. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Sumas's scale — its 8a band and its 268-day season. Your yard writes its own version of Sumas'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 Sumas’s own scale
6 of the readings below were taken at Sumas's own scale — its own ~268-day season between 28°F freezes, the 939 acres it covers and 462 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Sumas's own USDA hardiness band, zones 8aUSDA PHZM 2023
- Sumas's own 28°F hard-freeze dates, about Feb 27 and Nov 22 and the ~268-day span between themNOAA 1991–2020 Climate Normals
- 462 documented contamination sites on the federal record near Sumas, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Sumas's boundary and the 939 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 8a and a ~268-day seasonGrowable Ground crop-matching engine
- Sumas sits in the Puget Lowland — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Sumas's 939 acres read through its county's SSURGO summaryfrom Whatcom County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Whatcom County
- The growing challenges every Washington grower plans around — written at state scale, so they stay on the state guidefrom Washington
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Whatcom County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Sumas's 939 acreswhy one lot differs from the next →
- Which side of Sumas you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 939 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.2 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 Sumas-wide figureread your own land →
More in Washington
Growing region
Nearby growing guides