FrostList

When to Winterize Your Boat in Redwood City, CA

ON TRACK168 days until first 28°F freezeDec 26

In Redwood City, target December 19 to drain, antifreeze, and lay up the boat, about a week before the median first 28°F freeze of December 26; a surprise cold snap is exactly how freeze claims happen. Cold deepens quickly here — only about 14 days separate the first frost from that hard freeze.

OUTLOOK

Typical first first 28°F freeze near Dec 26; local deadline about Dec 19. The live 10-day outlook loads here.

Local freeze dates for Redwood City

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Nov 24Dec 12Jan 14
28°F (hard freeze)Dec 5Dec 26Jan 15

NOAA station: Redwood City · 0.6 mi away · 31 ft elevation.

Redwood City draws its numbers from Redwood City, 31 feet up and 0.6 miles away. Its median first-freeze dates are 32°F by Dec 12, 28°F by Dec 26. Year to year the 28°F date has ranged from Dec 5 to Jan 15 — about 41 days apart. Spring's last 32°F freeze clears around Jan 17.

In Redwood City, freezing nights (32°F) typically begin around Dec 12 and the first hard freeze (28°F) follows near Dec 26. That first freezing night has ranged from Nov 24 to Jan 14, roughly a 51-day spread. On the spring side, the last 32°F freeze clears around Jan 17 and as late as Feb 16 — the green light for reopening water and de-winterizing. With almost no snow in a normal year, cold — not plowing — sets the calendar, and it centers on Jan 17.

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

Against its neighbors, Redwood City (first freeze Dec 26) runs later than Palo Alto (Dec 22) and about a week ahead of Mountain View (Dec 31). Across California, local prep deadlines in our data range from Jan 9 to Dec 30, so a statewide rule of thumb would miss Redwood City by weeks. In Redwood City, that same cold is your cue to winterize an RV and store a motorcycle.

Other winter jobs in Redwood City

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

Sprinklers → Dec 16Frozen pipes → Nov 24Car battery → Dec 26Sump pump → Jan 17RV → Dec 16Motorcycle → Dec 12

See the full Redwood City 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 26 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 Redwood City, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.