FrostList

When to Winterize Your RV in Missoula, MT

ON TRACK93 days until first 28°F freezeOct 12

Missoula's deadline to winterize your RV is October 2: the local first 28°F freeze runs October 12 on average and September 28 at its earliest (1991–2020 normals). Plan for the early end: the one-in-ten date lands about 14 days before the median.

OUTLOOK

Typical first first 28°F freeze near Oct 12; local deadline about Oct 2. The live 10-day outlook loads here.

Local freeze dates for Missoula

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Sep 16Oct 1Oct 15
28°F (hard freeze)Sep 28Oct 12Oct 25
24°F (severe)Oct 7Oct 24Nov 10

NOAA station: Missoula 2 Ne · 1.9 mi away · 3,420 ft elevation.

For Missoula, the nearest NOAA station with freeze data is Missoula 2 Ne, 1.9 miles out at 3,420 feet. Median first-freeze dates there run 32°F by Oct 1, 28°F by Oct 12, 24°F by Oct 24. The 28°F freeze has come as early as Sep 28 and as late as Oct 25, a 27-day spread. Spring's last 32°F freeze clears around May 10. Snowfall averages 50 inches a year, first reaching an inch near November.

Missoula usually sees its first 32°F night about Oct 1, with the first 28°F hard freeze close behind near Oct 12. That first freezing night has ranged from Sep 16 to Oct 15, roughly a 29-day spread. On the spring side, the last 32°F freeze clears around May 10 and as late as May 28 — the green light for reopening water and de-winterizing. Snow totals near 50 inches a year mean plowing and ice-dam control share the winter to-do list here.

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

Missoula freezes later than Helena (Oct 7) and close to Great Falls (Oct 11) — a reminder that even nearby towns differ by days. Statewide, Montana prep dates run Sep 23 through Oct 2, which is why Missoula gets its own number rather than a Montana-wide average. The same freeze also decides when to shut down your sprinklers and winterize a boat.

Other winter jobs in Missoula

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

Sprinklers → Oct 2Frozen pipes → Sep 16Ice dams → Oct 16Car battery → Oct 12Snow blower → Oct 25Sump pump → May 10Boat → Oct 5Motorcycle → Oct 1

See the full Missoula 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 Missoula?
Wait until the last spring freeze has passed, which averages near May 10 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 Missoula 2 Ne, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.