FrostList

When to Winterize Your RV in Shoreline, WA

ON TRACK153 days until first 28°F freezeDec 11

Aim to winterize your RV in Shoreline by December 1, roughly a week and a half before the median first 28°F freeze of December 11, which one fall in ten shows up by November 17. It's a short step from frost to a hard freeze: roughly 18 days on average.

OUTLOOK

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

Local freeze dates for Shoreline

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Nov 4Nov 23Dec 16
28°F (hard freeze)Nov 17Dec 11Jan 17
24°F (severe)Nov 27Dec 24Feb 8

NOAA station: Seattle Sand Pt Wsfo · 6.2 mi away · 60 ft elevation.

The reference station for Shoreline is Seattle Sand Pt Wsfo (6.2 mi, 60 ft). First freeze there: 32°F by Nov 23, 28°F by Dec 11, 24°F by Dec 24. The 28°F freeze has come as early as Nov 17 and as late as Jan 17, a 61-day spread. Spring's last 32°F freeze clears around Mar 8. Snowfall averages 4 inches a year, first reaching an inch near December.

Expect the first frost near Nov 23 in Shoreline and the first hard freeze by about Dec 11. Year to year, the first 32°F night has fallen anywhere from Nov 4 to Dec 16 — about 42 days apart. Spring's final freeze lands near Mar 8 and as late as Mar 29, so that is when outdoor water and stored gear can safely come back online. Snow is light here, near 4 inches a year, so pipe and battery cold usually matters more than plowing.

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, Shoreline's first-freeze date near Dec 11 sits later than Edmonds (Dec 6) and close to Kirkland (Dec 11). Washington's deadlines span Oct 6 to Dec 1 statewide — one date for all of Washington would be off by weeks for Shoreline. Once you know Shoreline's freeze date, use it to shut down your sprinklers and winterize a boat too.

Other winter jobs in Shoreline

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

Sprinklers → Dec 1Frozen pipes → Nov 4Ice dams → Nov 15Car battery → Dec 11Snow blower → Nov 24Sump pump → Mar 8Boat → Dec 4Motorcycle → Nov 23

See the full Shoreline 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 Shoreline?
Wait until the last spring freeze has passed, which averages near Mar 8 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 Seattle Sand Pt Wsfo, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.