FrostList

When to Winterize Your RV in Milpitas, CA

ON TRACK170 days until first 28°F freezeDec 28

In a typical year, winterize your RV in Milpitas by December 18. The median first 28°F hard freeze at Milpitas's NOAA station is December 28 (1991–2020 normals); one year in ten it arrives as early as December 6. Plan for the early end: the one-in-ten date lands about 22 days before the median.

OUTLOOK

Typical first first 28°F freeze near Dec 28; local deadline about Dec 18. The live 10-day outlook loads here.

Local freeze dates for Milpitas

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Dec 1Dec 22Jan 20
28°F (hard freeze)Dec 6Dec 28Jan 14

NOAA station: San Jose · 5.2 mi away · 51 ft elevation.

The reference station for Milpitas is San Jose (5.2 mi, 51 ft). First freeze there: 32°F by Dec 22, 28°F by Dec 28. Year to year the 28°F date has ranged from Dec 6 to Jan 14 — about 39 days apart. Spring's last 32°F freeze clears around Jan 12.

Milpitas usually sees its first 32°F night about Dec 22, with the first 28°F hard freeze close behind near Dec 28. That first freezing night has ranged from Dec 1 to Jan 20, roughly a 50-day spread. On the spring side, the last 32°F freeze clears around Jan 12 and as late as Feb 14 — 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 12.

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

Compared with nearby cities, Milpitas's first-freeze date near Dec 28 sits close to Santa Clara (Dec 28) and close to Sunnyvale (Dec 31). California's deadlines span Jan 6 to Dec 27 statewide — one date for all of California would be off by weeks for Milpitas. Once you know Milpitas's freeze date, use it to shut down your sprinklers and winterize a boat too.

Other winter jobs in Milpitas

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

Sprinklers → Dec 18Frozen pipes → Dec 1Car battery → Dec 28Sump pump → Jan 12Boat → Dec 21Motorcycle → Dec 22

See the full Milpitas 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 Milpitas?
Wait until the last spring freeze has passed, which averages near Jan 12 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 Jose, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.