FrostList

When to Winterize Your RV in Lake Oswego, OR

ON TRACK150 days until first 28°F freezeDec 8

Aim to winterize your RV in Lake Oswego by November 28, roughly a week and a half before the median first 28°F freeze of December 8, which one fall in ten shows up by November 16. Cold deepens quickly here — only about 20 days separate the first frost from that hard freeze.

OUTLOOK

Typical first first 28°F freeze near Dec 8; local deadline about Nov 28. The live 10-day outlook loads here.

Local freeze dates for Lake Oswego

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Oct 30Nov 18Dec 12
28°F (hard freeze)Nov 16Dec 8Jan 5
24°F (severe)Nov 29Dec 26Feb 4

NOAA station: Oregon City · 5.5 mi away · 167 ft elevation.

The reference station for Lake Oswego is Oregon City (5.5 mi, 167 ft). First freeze there: 32°F by Nov 18, 28°F by Dec 8, 24°F by Dec 26. Year to year the 28°F date has ranged from Nov 16 to Jan 5 — about 50 days apart. Spring's last 32°F freeze clears around Mar 18. Snowfall averages 4 inches a year, first reaching an inch near January.

The freeze arrives in two steps in Lake Oswego: 32°F around Nov 18, then a hard 28°F near Dec 8. That first freezing night has ranged from Oct 30 to Dec 12, roughly a 43-day spread. On the spring side, the last 32°F freeze clears around Mar 18 and as late as Apr 11 — the green light for reopening water and de-winterizing. Only about 4 inches of snow falls in a typical year, so cold protection outranks snow removal.

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, Lake Oswego's first-freeze date near Dec 8 sits later than Tigard (Nov 30) and about a week ahead of Portland (Dec 20). Oregon's deadlines span Sep 24 to Dec 11 statewide — one date for all of Oregon would be off by weeks for Lake Oswego. Once you know Lake Oswego's freeze date, use it to shut down your sprinklers and winterize a boat too.

Other winter jobs in Lake Oswego

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

Sprinklers → Nov 28Frozen pipes → Oct 30Ice dams → Dec 16Car battery → Dec 8Snow blower → Dec 25Sump pump → Mar 18Boat → Dec 1Motorcycle → Nov 18

See the full Lake Oswego 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 Lake Oswego?
Wait until the last spring freeze has passed, which averages near Mar 18 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 Oregon City, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.