FrostList

When to Winterize Your Boat in New Berlin, WI

ON TRACK105 days until first 28°F freezeOct 24

In New Berlin, target October 17 to drain, antifreeze, and lay up the boat, about a week before the median first 28°F freeze of October 24; 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 Oct 24; local deadline about Oct 17. The live 10-day outlook loads here.

Local freeze dates for New Berlin

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Sep 30Oct 14Oct 26
28°F (hard freeze)Oct 8Oct 24Nov 6
24°F (severe)Oct 23Nov 4Nov 18

NOAA station: Hales Corners/Whitnall Park/Bo · 4.8 mi away · 774 ft elevation.

Numbers for New Berlin come from Hales Corners/Whitnall Park/Bo, 4.8 miles away at 774 feet, where the medians fall 32°F by Oct 14, 28°F by Oct 24, 24°F by Nov 4. That hard freeze has landed anywhere from Oct 8 to Nov 6, a swing of roughly 29 days. Spring's last 32°F freeze clears around May 3. Snowfall averages 52 inches a year, first reaching an inch near November.

The freeze arrives in two steps in New Berlin: 32°F around Oct 14, then a hard 28°F near Oct 24. That first freezing night has ranged from Sep 30 to Oct 26, roughly a 26-day spread. On the spring side, the last 32°F freeze clears around May 3 and as late as May 19 — 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

Compared with nearby cities, New Berlin's first-freeze date near Oct 24 sits close to Greenfield (Oct 24) and close to Brookfield (Oct 25). Wisconsin's deadlines span Oct 9 to Oct 30 statewide — one date for all of Wisconsin would be off by weeks for New Berlin. Once you know New Berlin's freeze date, use it to winterize an RV and store a motorcycle too.

Other winter jobs in New Berlin

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

Sprinklers → Oct 14Frozen pipes → Sep 30Ice dams → Oct 16Car battery → Oct 24Snow blower → Oct 25Sump pump → May 3RV → Oct 14Motorcycle → Oct 14

See the full New Berlin 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 Oct 24 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 Hales Corners/Whitnall Park/Bo, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.