FrostList

When to Winterize Your RV in Portland, ME

ON TRACK108 days until first 28°F freezeOct 27

Portland's deadline to winterize your RV is October 17: the local first 28°F freeze runs October 27 on average and October 14 at its earliest (1991–2020 normals). It's a short step from frost to a hard freeze: roughly 12 days on average.

OUTLOOK

Typical first first 28°F freeze near Oct 27; local deadline about Oct 17. The live 10-day outlook loads here.

Local freeze dates for Portland

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Oct 2Oct 15Oct 30
28°F (hard freeze)Oct 14Oct 27Nov 9
24°F (severe)Oct 26Nov 8Nov 23

NOAA station: Portland Intl Jetport · 2.4 mi away · 45 ft elevation.

For Portland, the nearest NOAA station with freeze data is Portland Intl Jetport, 2.4 miles out at 45 feet. Median first-freeze dates there run 32°F by Oct 15, 28°F by Oct 27, 24°F by Nov 8. The 28°F freeze has come as early as Oct 14 and as late as Nov 9, a 26-day spread. Spring's last 32°F freeze clears around Apr 26. Snowfall averages 69 inches a year, first reaching an inch near November.

Expect the first frost near Oct 15 in Portland and the first hard freeze by about Oct 27. Year to year, the first 32°F night has fallen anywhere from Oct 2 to Oct 30 — about 28 days apart. Spring's final freeze lands near Apr 26 and as late as May 7, so that is when outdoor water and stored gear can safely come back online. With about 69 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

Portland freezes about a week ahead of Augusta (Oct 31) and later than Concord (Oct 13) — a reminder that even nearby towns differ by days. Statewide, Maine prep dates run Oct 17 through Oct 21, which is why Portland gets its own number rather than a Maine-wide average. The same freeze also decides when to shut down your sprinklers and winterize a boat.

Other winter jobs in Portland

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

Sprinklers → Oct 17Frozen pipes → Oct 2Ice dams → Oct 16Car battery → Oct 27Snow blower → Oct 25Sump pump → Apr 26Boat → Oct 20Motorcycle → Oct 15

See the full Portland 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 Portland?
Wait until the last spring freeze has passed, which averages near Apr 26 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 Portland Intl Jetport, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.