FrostList

When to Winterize Your Boat in Beloit, WI

ON TRACK104 days until first 28°F freezeOct 23

In Beloit, target October 16 to drain, antifreeze, and lay up the boat, about a week before the median first 28°F freeze of October 23; a surprise cold snap is exactly how freeze claims happen. With about a 26-day spread, the date holds fairly steady from year to year.

OUTLOOK

Typical first first 28°F freeze near Oct 23; local deadline about Oct 16. The live 10-day outlook loads here.

Local freeze dates for Beloit

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Sep 28Oct 12Oct 24
28°F (hard freeze)Oct 9Oct 23Nov 4
24°F (severe)Oct 20Nov 2Nov 17

NOAA station: Beloit · 0.3 mi away · 788 ft elevation.

Numbers for Beloit come from Beloit, 0.3 miles away at 788 feet, where the medians fall 32°F by Oct 12, 28°F by Oct 23, 24°F by Nov 2. That hard freeze has landed anywhere from Oct 9 to Nov 4, a swing of roughly 26 days. Spring's last 32°F freeze clears around May 1. Snowfall averages 36 inches a year, first reaching an inch near November.

In Beloit, freezing nights (32°F) typically begin around Oct 12 and the first hard freeze (28°F) follows near Oct 23. Year to year, the first 32°F night has fallen anywhere from Sep 28 to Oct 24 — about 26 days apart. Spring's final freeze lands near May 1 and as late as May 16, so that is when outdoor water and stored gear can safely come back online. Snowfall averages roughly 36 inches a year — enough that a working snow blower and a clear roof edge earn their keep.

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, Beloit's first-freeze date near Oct 23 sits close to Janesville (Oct 26) and about a week ahead of Rockford (Oct 28). Wisconsin's deadlines span Oct 9 to Oct 30 statewide — one date for all of Wisconsin would be off by weeks for Beloit. Once you know Beloit's freeze date, use it to winterize an RV and store a motorcycle too.

Other winter jobs in Beloit

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

Sprinklers → Oct 13Frozen pipes → Sep 28Ice dams → Oct 16Car battery → Oct 23Snow blower → Oct 25Sump pump → May 1RV → Oct 13Motorcycle → Oct 12

See the full Beloit 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 23 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 Beloit, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.