FrostList

When to Winterize Your RV in Vacaville, CA

ON TRACK152 days until first 28°F freezeDec 10

Vacaville's median first 28°F hard freeze is December 10 (1991–2020 NOAA normals), and it can strike as early as November 24 — so winterize your RV in Vacaville by November 30. It's a short step from frost to a hard freeze: roughly 12 days on average.

OUTLOOK

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

Local freeze dates for Vacaville

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Nov 12Nov 28Dec 18
28°F (hard freeze)Nov 24Dec 10Jan 11
24°F (severe)Dec 3Dec 21Jan 17

NOAA station: Vacaville Nut Tree AP · 2.2 mi away · 109 ft elevation.

The reference station for Vacaville is Vacaville Nut Tree AP (2.2 mi, 109 ft). First freeze there: 32°F by Nov 28, 28°F by Dec 10, 24°F by Dec 21. That hard freeze has landed anywhere from Nov 24 to Jan 11, a swing of roughly 48 days. Spring's last 32°F freeze clears around Feb 18.

Vacaville usually sees its first 32°F night about Nov 28, with the first 28°F hard freeze close behind near Dec 10. Year to year, the first 32°F night has fallen anywhere from Nov 12 to Dec 18 — about 36 days apart. Spring's final freeze lands near Feb 18 and as late as Mar 25, so that is when outdoor water and stored gear can safely come back online. Measurable snow is rare, so the freeze near Feb 18 — not snow load — drives the local prep list.

Your rv checklist

  1. Drain the fresh, gray, and black tanks, then drain the water heater only after it has cooled and lost pressure.
  2. Bypass the water heater so you do not waste six gallons of antifreeze filling the tank.
  3. Blow out the lines with a compressor at about 30–40 psi, then pump non-toxic RV antifreeze through every faucet until it runs pink.
    Helpful gear: RV antifreeze (6-pack) — Recommended pick
  4. Use a water-pump converter kit to draw antifreeze straight from the jug through the plumbing.
    Helpful gear: Water pump converter kit — Recommended pick
  5. Pour a cup of antifreeze into each drain trap and the toilet to protect the seals.
  6. Fit a blow-out plug at the city-water inlet so you can clear that line too.
    Helpful gear: Blow-out plug — Recommended pick
  7. Remove batteries or put them on a maintainer, and store them off a cold concrete floor.
  8. Cover roof vents, close the propane, and set out traps or deterrents so mice do not move in.

What to have on hand

RV antifreeze (6-pack)
Non-toxic pink fluid for the fresh-water plumbing and traps.
Recommended pick
Water pump converter kit
Siphon kit that draws antifreeze straight through the pump.
Recommended pick
Blow-out plug
Adapter that lets a compressor clear the lines before antifreeze.
Recommended pick
Heated fresh-water hose
For anyone staying hooked up through a cold snap.
Recommended pick

What this means locally

Vacaville freezes about a week ahead of Fairfield (Dec 24) and about a week ahead of Napa (Dec 19) — a reminder that even nearby towns differ by days. Statewide, California prep dates run Jan 6 through Dec 27, which is why Vacaville gets its own number rather than a California-wide average. The same freeze also decides when to shut down your sprinklers and winterize a boat.

Other winter jobs in Vacaville

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

Sprinklers → Nov 30Frozen pipes → Nov 12Car battery → Dec 10Sump pump → Feb 18Boat → Dec 3Motorcycle → Nov 28

See the full Vacaville winter checklist, in order →

Frequently asked questions

At what temperature do RV pipes freeze?
An RV's exposed plumbing and thin-walled tanks can begin to freeze once temperatures sit in the mid-20s for a few hours, sooner than a house because there is little insulation around the lines. That is why the winterizing deadline tracks the first 28°F freeze rather than the first light frost.
How much RV antifreeze do I need?
Most travel trailers and motorhomes take about two to three gallons of non-toxic RV antifreeze, and larger rigs more. Bypassing the water heater saves roughly six gallons you would otherwise waste filling the tank. Buy an extra jug; stores sell out once the first freeze warnings hit.
Can I just use my RV furnace instead of winterizing?
Relying on the furnace is risky. A propane run-out, a tripped breaker, or a dead battery during a cold night leaves the plumbing unprotected, and the furnace may not keep the underbelly and bays warm enough anyway. Draining and adding antifreeze is the dependable way to protect the system.
How do I winterize an RV water heater?
Let the tank cool and lose pressure, then drain it and, if fitted, pull the anode rod. Do not add antifreeze to the water heater tank; instead, set the bypass valves so antifreeze skips the tank and fills only the lines. Fresh antifreeze in an unbypassed heater just wastes several gallons.
When is it safe to de-winterize an RV in Vacaville?
Wait until the last spring freeze has passed, which averages near Feb 18 here. De-winterize by flushing the antifreeze from the lines, sanitizing the fresh tank, and checking for leaks before a trip. Reopening too early risks a surprise late freeze on a charged system.
Do I need to winterize an RV stored indoors?
A reliably heated indoor space that stays above freezing protects the plumbing, so full winterizing may not be needed. But an unheated garage or barn can still drop below freezing on a cold night. If you cannot guarantee the space stays warm, winterize to be safe.

Data: NOAA 1991–2020 normals via Vacaville Nut Tree AP, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.