FrostList

When to Winterize Your RV in Great Falls, MT

ON TRACK92 days until first 28°F freezeOct 11

Aim to winterize your RV in Great Falls by October 1, roughly a week and a half before the median first 28°F freeze of October 11, which one fall in ten shows up by September 25. Year to year the date swings about 34 days, which is why the live outlook beats the calendar.

OUTLOOK

Typical first first 28°F freeze near Oct 11; local deadline about Oct 1. The live 10-day outlook loads here.

Local freeze dates for Great Falls

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Sep 17Oct 1Oct 16
28°F (hard freeze)Sep 25Oct 11Oct 29
24°F (severe)Oct 2Oct 24Nov 8

NOAA station: Great Falls 16St · 0.5 mi away · 3,505 ft elevation.

Numbers for Great Falls come from Great Falls 16St, 0.5 miles away at 3,505 feet, where the medians fall 32°F by Oct 1, 28°F by Oct 11, 24°F by Oct 24. The 28°F freeze has come as early as Sep 25 and as late as Oct 29, a 34-day spread. Spring's last 32°F freeze clears around May 6. Snowfall averages 66 inches a year, first reaching an inch near October.

The freeze arrives in two steps in Great Falls: 32°F around Oct 1, then a hard 28°F near Oct 11. Year to year, the first 32°F night has fallen anywhere from Sep 17 to Oct 16 — about 29 days apart. Spring's final freeze lands near May 6 and as late as May 19, so that is when outdoor water and stored gear can safely come back online. With about 66 inches of snow a year, roof, snow-blower, and ice-dam prep all belong on the same calendar.

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, Great Falls's first-freeze date near Oct 11 sits later than Helena (Oct 7) and later than Bozeman (Oct 3). Montana's deadlines span Sep 23 to Oct 2 statewide — one date for all of Montana would be off by weeks for Great Falls. Once you know Great Falls's freeze date, use it to shut down your sprinklers and winterize a boat too.

Other winter jobs in Great Falls

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

Sprinklers → Oct 1Frozen pipes → Sep 17Ice dams → Sep 15Car battery → Oct 11Snow blower → Sep 24Sump pump → May 6Boat → Oct 4Motorcycle → Oct 1

See the full Great Falls 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 Great Falls?
Wait until the last spring freeze has passed, which averages near May 6 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 Great Falls 16St, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.