FrostList

When to Winterize Your Boat in St. George, UT

ON TRACK132 days until first 28°F freezeNov 20

Freeze protection for a St. George boat keys off the first 28°F freeze, which averages November 20, so haul out and winterize by November 13 to beat it. It's a short step from frost to a hard freeze: roughly 10 days on average.

OUTLOOK

Typical first first 28°F freeze near Nov 20; local deadline about Nov 13. The live 10-day outlook loads here.

Local freeze dates for St. George

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Oct 27Nov 10Nov 22
28°F (hard freeze)Nov 7Nov 20Dec 3
24°F (severe)Nov 18Dec 1Dec 18

NOAA station: St George · 2.6 mi away · 2,857 ft elevation.

For St. George, the nearest NOAA station with freeze data is St George, 2.6 miles out at 2,857 feet. Median first-freeze dates there run 32°F by Nov 10, 28°F by Nov 20, 24°F by Dec 1. The 28°F freeze has come as early as Nov 7 and as late as Dec 3, a 26-day spread. Spring's last 32°F freeze clears around Mar 14. Snowfall averages 1 inches a year.

Expect the first frost near Nov 10 in St. George and the first hard freeze by about Nov 20. Year to year, the first 32°F night has fallen anywhere from Oct 27 to Nov 22 — about 26 days apart. Spring's final freeze lands near Mar 14 and as late as Apr 6, so that is when outdoor water and stored gear can safely come back online. Measurable snow is rare, so the freeze near Mar 14 — not snow load — drives the local prep list.

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, St. George's first-freeze date near Nov 20 sits about a week ahead of North Las Vegas (Dec 21) and about a week ahead of Henderson (Dec 26). Utah's deadlines span Oct 7 to Nov 13 statewide — one date for all of Utah would be off by weeks for St. George. Once you know St. George's freeze date, use it to winterize an RV and store a motorcycle too.

Other winter jobs in St. George

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

Sprinklers → Nov 10Frozen pipes → Oct 27Car battery → Nov 20Sump pump → Mar 14RV → Nov 10Motorcycle → Nov 10

See the full St. George 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 20 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 UT 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 St George, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.