FrostList

When to Winterize Your Boat in West Allis, WI

ON TRACK113 days until first 28°F freezeNov 1

In West Allis, target October 25 to drain, antifreeze, and lay up the boat, about a week before the median first 28°F freeze of November 1; a surprise cold snap is exactly how freeze claims happen. Cold deepens quickly here — only about 10 days separate the first frost from that hard freeze.

OUTLOOK

Typical first first 28°F freeze near Nov 1; local deadline about Oct 25. The live 10-day outlook loads here.

Local freeze dates for West Allis

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Oct 7Oct 22Nov 3
28°F (hard freeze)Oct 19Nov 1Nov 14
24°F (severe)Nov 1Nov 11Nov 25

NOAA station: West Allis · 0.3 mi away · 723 ft elevation.

Numbers for West Allis come from West Allis, 0.3 miles away at 723 feet, where the medians fall 32°F by Oct 22, 28°F by Nov 1, 24°F by Nov 11. That hard freeze has landed anywhere from Oct 19 to Nov 14, a swing of roughly 26 days. Spring's last 32°F freeze clears around Apr 26. Snowfall averages 52 inches a year, first reaching an inch near November.

In West Allis, freezing nights (32°F) typically begin around Oct 22 and the first hard freeze (28°F) follows near Nov 1. That first freezing night has ranged from Oct 7 to Nov 3, roughly a 27-day spread. On the spring side, the last 32°F freeze clears around Apr 26 and as late as May 12 — the green light for reopening water and de-winterizing. Snow totals near 52 inches a year mean plowing and ice-dam control share the winter to-do list here.

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

West Allis freezes close to Wauwatosa (Oct 30) and later than Greenfield (Oct 24) — a reminder that even nearby towns differ by days. Statewide, Wisconsin prep dates run Oct 9 through Oct 30, which is why West Allis gets its own number rather than a Wisconsin-wide average. The same freeze also decides when to winterize an RV and store a motorcycle.

Other winter jobs in West Allis

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

Sprinklers → Oct 22Frozen pipes → Oct 7Ice dams → Oct 16Car battery → Nov 1Snow blower → Oct 25Sump pump → Apr 26RV → Oct 22Motorcycle → Oct 22

See the full West Allis 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 Nov 1 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 WI 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 West Allis, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.