FrostList

When to Winterize Your Boat in Bloomington, IL

ON TRACK111 days until first 28°F freezeOct 30

Plan to haul out and winterize your boat in Bloomington by October 23. The first 28°F freeze near Bloomington averages October 30 in the 1991–2020 normals, and freeze damage often surprises owners in milder states. It's a short step from frost to a hard freeze: roughly 10 days on average.

OUTLOOK

Typical first first 28°F freeze near Oct 30; local deadline about Oct 23. The live 10-day outlook loads here.

Local freeze dates for Bloomington

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Oct 9Oct 20Nov 1
28°F (hard freeze)Oct 18Oct 30Nov 11
24°F (severe)Oct 28Nov 8Nov 23

NOAA station: Bloomington 5W · 4.9 mi away · 852 ft elevation.

Numbers for Bloomington come from Bloomington 5W, 4.9 miles away at 852 feet, where the medians fall 32°F by Oct 20, 28°F by Oct 30, 24°F by Nov 8. That hard freeze has landed anywhere from Oct 18 to Nov 11, a swing of roughly 24 days. Spring's last 32°F freeze clears around Apr 21. Snowfall averages 20 inches a year, first reaching an inch near December.

Bloomington usually sees its first 32°F night about Oct 20, with the first 28°F hard freeze close behind near Oct 30. Year to year, the first 32°F night has fallen anywhere from Oct 9 to Nov 1 — about 23 days apart. Spring's final freeze lands near Apr 21 and as late as May 5, so that is when outdoor water and stored gear can safely come back online. Snowfall averages roughly 20 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

Bloomington freezes close to Normal (Oct 27) and close to Peoria (Nov 2) — a reminder that even nearby towns differ by days. Statewide, Illinois prep dates run Oct 17 through Nov 8, which is why Bloomington gets its own number rather than a Illinois-wide average. The same freeze also decides when to winterize an RV and store a motorcycle.

Other winter jobs in Bloomington

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

Sprinklers → Oct 20Frozen pipes → Oct 9Ice dams → Nov 15Car battery → Oct 30Snow blower → Nov 24Sump pump → Apr 21RV → Oct 20Motorcycle → Oct 20

See the full Bloomington 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 30 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 IL 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 Bloomington 5W, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.