FrostList

When to Winterize Your Boat in Chico, CA

ON TRACK145 days until first 28°F freezeDec 3

Freeze protection for a Chico boat keys off the first 28°F freeze, which averages December 3, so haul out and winterize by November 26 to beat it. The early-to-late range spans roughly 53 days, so treat the median as a midpoint, not a promise.

OUTLOOK

Typical first first 28°F freeze near Dec 3; local deadline about Nov 26. The live 10-day outlook loads here.

Local freeze dates for Chico

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Nov 1Nov 17Dec 5
28°F (hard freeze)Nov 13Dec 3Jan 5
24°F (severe)Nov 28Dec 22Jan 18

NOAA station: Chico Univ Farm · 2.7 mi away · 185 ft elevation.

Numbers for Chico come from Chico Univ Farm, 2.7 miles away at 185 feet, where the medians fall 32°F by Nov 17, 28°F by Dec 3, 24°F by Dec 22. That hard freeze has landed anywhere from Nov 13 to Jan 5, a swing of roughly 53 days. Spring's last 32°F freeze clears around Mar 4. Snowfall averages 0 inches a year.

Expect the first frost near Nov 17 in Chico and the first hard freeze by about Dec 3. The 32°F date swings from Nov 1 at its earliest to Dec 5 at its latest, near 34 days. The last spring freeze averages Mar 4 and as late as Apr 2, which sets the safe window for reopening outdoor water and de-winterizing gear. Snow barely registers here; the freeze date, around Mar 4, is the one that matters.

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

Chico freezes about a week ahead of Yuba City (Dec 24) and about a week ahead of Lincoln (Dec 22) — a reminder that even nearby towns differ by days. Statewide, California prep dates run Jan 9 through Dec 30, which is why Chico gets its own number rather than a California-wide average. The same freeze also decides when to winterize an RV and store a motorcycle.

Other winter jobs in Chico

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

Sprinklers → Nov 23Frozen pipes → Nov 1Car battery → Dec 3Sump pump → Mar 4RV → Nov 23Motorcycle → Nov 17

See the full Chico 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 Dec 3 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 CA 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 Chico Univ Farm, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.