FrostList

When to Winterize Your Boat in Bellevue, WA

ON TRACK153 days until first 28°F freezeDec 11

Plan to haul out and winterize your boat in Bellevue by December 4. The first 28°F freeze near Bellevue averages December 11 in the 1991–2020 normals, and freeze damage often surprises owners in milder states. The early-to-late range spans roughly 61 days, so treat the median as a midpoint, not a promise.

OUTLOOK

Typical first first 28°F freeze near Dec 11; local deadline about Dec 4. The live 10-day outlook loads here.

Local freeze dates for Bellevue

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Nov 4Nov 23Dec 16
28°F (hard freeze)Nov 17Dec 11Jan 17
24°F (severe)Nov 27Dec 24Feb 8

NOAA station: Seattle Sand Pt Wsfo · 5.9 mi away · 60 ft elevation.

For Bellevue, the nearest NOAA station with freeze data is Seattle Sand Pt Wsfo, 5.9 miles out at 60 feet. Median first-freeze dates there run 32°F by Nov 23, 28°F by Dec 11, 24°F by Dec 24. Year to year the 28°F date has ranged from Nov 17 to Jan 17 — about 61 days apart. Spring's last 32°F freeze clears around Mar 8. Snowfall averages 4 inches a year, first reaching an inch near December.

Expect the first frost near Nov 23 in Bellevue and the first hard freeze by about Dec 11. The 32°F date swings from Nov 4 at its earliest to Dec 16 at its latest, near 42 days. The last spring freeze averages Mar 8 and as late as Mar 29, which sets the safe window for reopening outdoor water and de-winterizing gear. At about 4 inches of snow a year, the freeze — not snow load — is the thing to plan around.

Your boat checklist

  1. Change the engine oil and filter while the motor is warm so contaminants leave with the old oil.
  2. Run the engine on antifreeze until pink fluid reaches the outlet, protecting the block and manifolds.
    Helpful gear: Marine antifreeze — Recommended pick
  3. Fog the cylinders with fogging oil as the engine runs down to coat internal parts against corrosion.
    Helpful gear: Fogging oil — Recommended pick
  4. Top off the fuel tank and add stabilizer to limit condensation and protect ethanol-blend fuel.
    Helpful gear: Marine fuel stabilizer — Recommended pick
  5. Drain the raw-water system, the livewell, and any washdown lines that can trap water.
  6. Remove the battery, charge it fully, and keep it on a maintainer over the layup.
    Helpful gear: Battery maintainer — Recommended pick
  7. Support the cover so snow and rain shed off, and leave vents so the interior can breathe.
  8. For an inboard or sterndrive, follow the manual closely — those blocks are the ones freeze claims hit hardest.

What to have on hand

Marine antifreeze
Propylene-glycol fluid rated for engine blocks and systems.
Recommended pick
Marine fuel stabilizer
Additive that protects ethanol-blend fuel over the layup.
Recommended pick
Fogging oil
Spray that coats cylinders against corrosion in storage.
Recommended pick
Battery maintainer
Keeps the cranking battery topped off on the trailer.
Recommended pick

What this means locally

Bellevue freezes close to Kirkland (Dec 11) and close to Redmond (Dec 11) — a reminder that even nearby towns differ by days. Statewide, Washington prep dates run Oct 9 through Dec 4, which is why Bellevue gets its own number rather than a Washington-wide average. The same freeze also decides when to winterize an RV and store a motorcycle.

Other winter jobs in Bellevue

Every task below is dated to Bellevue's own freeze and snow normals.

Sprinklers → Dec 1Frozen pipes → Nov 4Ice dams → Nov 15Car battery → Dec 11Snow blower → Nov 24Sump pump → Mar 8RV → Dec 1Motorcycle → Nov 23

See the full Bellevue winter checklist, in order →

Frequently asked questions

At what temperature does a boat engine block crack?
Trapped water in an engine block or manifold can freeze and crack the casting once temperatures fall below 32°F and stay there long enough. Inboard and sterndrive blocks hold the most water and are the most vulnerable. Draining fully and adding antifreeze before the first hard freeze near Dec 11 is the protection.
Do outboards need winterizing?
Yes. An outboard should be drained so no water sits in the powerhead or lower unit, and the fuel system stabilized. Outboards self-drain better than inboards when tilted down, but fogging the cylinders and changing the gear oil are still part of a proper layup.
Fogging oil: is it necessary?
Fogging coats the cylinder walls and internal parts with a film that resists corrosion during months of storage. On engines that sit all winter it is cheap insurance against rust, especially in humid or coastal storage. Follow your engine maker's guidance on how to apply it.
How much does boat winterization cost?
A professional winterization varies with engine type and boat size, and inboards cost more than a simple outboard. Doing it yourself costs mainly antifreeze, oil, and fogging oil. Either way, the bill is far smaller than repairing a cracked block, which is the failure winterizing prevents.
Do boats in WA really need winterizing?
If temperatures reach freezing where the boat is stored, yes. Freeze claims are common in milder states precisely because owners assume they are safe and skip the step, then a rare cold snap cracks a block. Check the local freeze dates above and protect the engine before the first hard freeze.
When should I de-winterize my boat?
De-winterize in spring once the risk of a hard freeze has passed for your area. Reconnect and charge the battery, replace drain plugs, check hoses and clamps, and inspect the fuel system before the first launch. Reopening too early leaves the block exposed to a late cold snap.

Data: NOAA 1991–2020 normals via Seattle Sand Pt Wsfo, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.