Mill Creek, Washington, sits in USDA hardiness zone 9a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Crops well matched to these conditions include kale, potato, garlic, and western red cedar — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Mill Creek, 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 Mill Creek 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 Mill Creek — soil, climate, flood, and parcel records. How we handle your address.
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Mill Creek — the short answer
Mill Creek, Washington: USDA zone 9a, about 208 days between hard freezes, across 3K acres of city.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 15
- Snohomish County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Nov 9
- Snohomish County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~208
- Snohomish County normal — NOAA 1991–2020, nearest to this town
- City area
- 3K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. No 30-year normal resolves at this town’s own centroid, so the hard-freeze dates are Snohomish County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9a is Mill Creek's average, not your lot's — a low corner or a tree line moves it. Against Mill Creek's 208-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Mill Creek
Each reading below is measured for Mill Creek itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsMill Creek runs about 208 days between hard freezes (read from Snohomish County, the closest normal to Mill Creek) — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredMill Creek sits in USDA hardiness zone 9a.
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 Mill Creek is in
Mill Creek sits in the Puget Lowland — EPA Level III, inside the wider Marine West Coast Forest. That is read at Mill Creek's own centroid, and it is not what its county reads: Snohomish County is mostly North Cascades. The wider page above you is answering a different question about different ground.
What Grows in Mill Creek
Plants matched to Mill Creek's USDA zones 9a, ordered by how much hardiness margin each has here — the ones with room to spare at both ends of this town's band lead. Each links to its full growing profile.
Is it too late to plant in Mill Creek?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 18; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 9 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
What's on the federal record near Mill Creek
Closest first, within ~10 miles of Mill Creek. Listing isn't leaking, and distance isn't exposure.
- MILL CREEK COMMUNITY ASSOCIATIONUnderground Storage Tanks · 0.7 mi
- 28N/05E-31F01Nitrate · 0.7 mi
- UNITED DEVELOPMENTUnderground Storage Tanks · 0.7 mi
- 27N/05E-06F02Nitrate · 0.7 mi
- SPROUTS FARMERS MARKET 456Brownfields · 0.8 mi
- MILL CREEK SHELLUnderground Storage Tanks · 0.8 mi
- SILVER LAKE WATER DISTRICTUnderground Storage Tanks · 0.8 mi
- HUNTRON INCBrownfields · 0.8 mi
- CIRCLE K CONVENIENCE STORE 8567Underground Storage Tanks · 0.9 mi
- S & S PETROLEUM INCUnderground Storage Tanks · 0.9 mi
- NORTH SOUND DERMATOLOGY LABORATORYBrownfields · 0.9 mi
- LOWES HOME CENTERS LLC 1573Brownfields · 0.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Mill Creek'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 Mill Creek.
Total Sites
1,713
within ~10 miles of Mill Creek
Risk Level
Elevated
Highest-severity
5 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Mill Creek
Severity Distribution
within ~10 miles of Mill Creek
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Mill Creek
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 Mill Creek average
Your land is one point inside Mill Creek
Everything above resolves to Mill Creek as a whole — one PHZM band, read across 3K acres, with hard-freeze dates borrowed from Snohomish County’s record because no 30-year normal resolves at this city’s own centroid. 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 Mill Creek Average
Mill Creek Average
- ●USDA Zones 9a, averaged across Mill Creek
- ●One soil character for all of Mill Creek
- ●Frost dates read at Mill Creek's scale: Apr 15 to Nov 9
YOUR Parcel
- ✓Your exact zone, not Mill Creek's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Mill Creek
Pull a site-specific report for your exact address in Mill Creek, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mill Creek averages can't show:
We read public map data around Mill Creek — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mill Creek average
How we know this about Mill Creek
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 Snohomish County’s record, because none resolves here; 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 Mill Creek
When does frost risk typically end in Mill Creek?
The last hard freeze (28°F) in Mill Creek typically lands around Apr 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 May 6.
When is the first frost in Mill Creek?
The first hard freeze (28°F) in Mill Creek typically arrives around Nov 9, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 26, so the watching starts about Oct 10 — about 208 days after the spring freeze cleared.
How long is the growing season in Mill Creek?
Measured between 28°F hard freezes, Mill Creek sees about 208 frost-free days — roughly Apr 15 through Nov 9, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 6 to Oct 26, about 173 days.
Is the soil safe to grow vegetables in Mill Creek?
The federal record around Mill Creek is a meaningful one — 1,713 documented sites, mostly Underground Storage Tanks entries (1,013), the nearest Underground Storage Tanks record about 0.7 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 Mill Creek?
From about Oct 10 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 9 (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 9. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Mill Creek's scale — its 9a band and its 208-day season. Your yard writes its own version of Mill Creek'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 Mill Creek’s own scale
4 of the readings below were taken at Mill Creek's own scale — the 2,972 acres it covers and 1,713 documented sites around it; 6 are borrowed from a wider read, named and linked below.
Measured here
- Mill Creek's own USDA hardiness band, zones 9aUSDA PHZM 2023
- 1,713 documented contamination sites on the federal record near Mill Creek, the closest Underground Storage Tanks record about 0.7 miles out from the town centreFederal environmental registers
- Mill Creek's boundary and the 2,972 acres inside itUS Census TIGER/Line 2025
- Mill Creek sits in the Puget Lowland — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Mill Creek has no normal of its own, so its county's is the closest measured readfrom Snohomish County
- Soil character — no town-scale survey exists, so Mill Creek's 2,972 acres read through its county's SSURGO summaryfrom Snohomish County
- The candidate plant list — Washington's curated set, filtered to this zone band and re-ordered by how much margin each has herefrom Washington
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Snohomish 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 Snohomish County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Mill Creek's 2,972 acreswhy one lot differs from the next →
- Which side of Mill Creek you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,972 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.7 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 Mill Creek-wide figureread your own land →