FrostList

When to Winterize Your RV in San Luis Obispo, CA

SEASON PASSED179 days until first 28°F freezeJan 6

San Luis Obispo's median first 28°F hard freeze is January 6 (1991–2020 NOAA normals), and it can strike as early as December 14 — so winterize your RV in San Luis Obispo by December 27. Plan for the early end: the one-in-ten date lands about 23 days before the median.

OUTLOOK

Typical first first 28°F freeze near Jan 6; local deadline about Dec 27. The live 10-day outlook loads here.

Local freeze dates for San Luis Obispo

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Nov 25Dec 25Feb 12
28°F (hard freeze)Dec 14Jan 6Feb 17

NOAA station: San Luis Obispo Poly · 1.6 mi away · 308 ft elevation.

The reference station for San Luis Obispo is San Luis Obispo Poly (1.6 mi, 308 ft). First freeze there: 32°F by Dec 25, 28°F by Jan 6. That hard freeze has landed anywhere from Dec 14 to Feb 17, a swing of roughly 65 days. Spring's last 32°F freeze clears around Jan 16.

Expect the first frost near Dec 25 in San Luis Obispo and the first hard freeze by about Jan 6. That first freezing night has ranged from Nov 25 to Feb 12, roughly a 79-day spread. On the spring side, the last 32°F freeze clears around Jan 16 and as late as Feb 26 — 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 16.

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

Against its neighbors, San Luis Obispo (first freeze Jan 6) runs about a week ahead of Santa Maria (Dec 27) and about a week ahead of Lompoc (Dec 29). Across California, local prep deadlines in our data range from Jan 6 to Dec 27, so a statewide rule of thumb would miss San Luis Obispo by weeks. In San Luis Obispo, that same cold is your cue to shut down your sprinklers and winterize a boat.

Other winter jobs in San Luis Obispo

Every task below is dated to San Luis Obispo's own freeze and snow normals.

Sprinklers → Dec 27Frozen pipes → Nov 25Car battery → Jan 6Sump pump → Jan 16Boat → Dec 30Motorcycle → Dec 25

See the full San Luis Obispo 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 San Luis Obispo?
Wait until the last spring freeze has passed, which averages near Jan 16 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 San Luis Obispo Poly, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.