FrostList

When to Winterize Your RV in Casper, WY

ON TRACK87 days until first 28°F freezeOct 6

Casper's median first 28°F hard freeze is October 6 (1991–2020 NOAA normals), and it can strike as early as September 21 — so winterize your RV in Casper by September 26. The early-to-late range spans roughly 32 days, so treat the median as a midpoint, not a promise.

OUTLOOK

Typical first first 28°F freeze near Oct 6; local deadline about Sep 26. The live 10-day outlook loads here.

Local freeze dates for Casper

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Sep 14Sep 29Oct 12
28°F (hard freeze)Sep 21Oct 6Oct 23
24°F (severe)Sep 30Oct 17Nov 1

NOAA station: Casper Wwtp · 1.1 mi away · 5,097 ft elevation.

The reference station for Casper is Casper Wwtp (1.1 mi, 5,097 ft). First freeze there: 32°F by Sep 29, 28°F by Oct 6, 24°F by Oct 17. Year to year the 28°F date has ranged from Sep 21 to Oct 23 — about 32 days apart. Spring's last 32°F freeze clears around May 10. Snowfall averages 72 inches a year, first reaching an inch near September.

Expect the first frost near Sep 29 in Casper and the first hard freeze by about Oct 6. Year to year, the first 32°F night has fallen anywhere from Sep 14 to Oct 12 — about 28 days apart. Spring's final freeze lands near May 10 and as late as May 24, so that is when outdoor water and stored gear can safely come back online. With about 72 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

Against its neighbors, Casper (first freeze Oct 6) runs about a week ahead of Cheyenne (Oct 10) and about a week ahead of Fort Collins (Oct 17). Across Wyoming, local prep deadlines in our data range from Sep 26 to Sep 30, so a statewide rule of thumb would miss Casper by weeks. In Casper, that same cold is your cue to shut down your sprinklers and winterize a boat.

Other winter jobs in Casper

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

Sprinklers → Sep 26Frozen pipes → Sep 14Ice dams → Aug 16Car battery → Oct 6Snow blower → Aug 25Sump pump → May 10Boat → Sep 29Motorcycle → Sep 29

See the full Casper 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 Casper?
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 Casper Wwtp, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.