To keep pipes from freezing, drain the outdoor faucets and insulate exposed pipes before winter, keep the heat at 55°F or higher even when you're away, and take extra care when the forecast drops toward 20°F. Here is which pipes freeze first, what to do before and during a cold snap, and what to do if a pipe freezes anyway.
The ones cold air can reach. The Red Cross lists:
Gaps in the house make it worse. The University of Illinois study behind the 20°F rule of thumb (below) found that holes in a house's outer shell "can play a major role for pipes that would otherwise appear protected".
There's no single number, but 20°F outside is a common warning level for exposed, uninsulated pipes. It comes from field tests by the University of Illinois Building Research Council: an uninsulated pipe in a vented, unheated attic started to freeze "just at or below 20 °F" outside, and the report proposed 20°F as an alert threshold for the southern United States (Research Report 96-1, 1996). A Virginia utility, the James City Service Authority, says the same: "you should begin to worry about uninsulated pipes when the outdoor temperature is 20 degrees" (James City County).
Treat 20°F as the point where the risk rises, not as a safe line. The same report expected "isolated, infrequent, freezing incidents" at overnight temperatures between 20 and 32°F, mostly where drafts reach a pipe.
On the calendar, the first hard freeze (28°F) comes on average around November 4 on the Dulles side (western Fairfax, Loudoun, Prince William) and December 3 near Reagan National (Arlington, Alexandria), according to NOAA's 1991–2020 normals for Dulles and Reagan National.
Do it before the first hard freeze. Earlier is safer, since those dates are averages.
Shut down and drain the sprinkler system at the same time, the way its manual says. If you can't find an inside shut-off, the valve won't close fully, or the faucet still drips once it's off, book plumbing repair before the freeze.
Winterizing outdoor faucets is one item on the broader fall home maintenance checklist worth working through before the cold sets in.
Fit pipe insulation on the pipes in the crawl space, garage, attic and any unheated basement, and on pipes that run along outside walls.
Look where pipes pass through outside walls and floors, and around crawl-space access doors and basement windows. Small gaps can be caulked or foamed. For a lot of gaps, or ones that are hard to reach, book sealing drafts and gaps.
If a pipe bursts, closing the main valve is how you stop the water. Find it now, label it, and show everyone at home how to close it. If it's stuck, leaks or can't be found, have a plumber look at it before winter.
The first three steps come from the Red Cross (as of September 2026):
A faucet that gives only a trickle, or nothing, on a freezing morning often means a frozen pipe.
Close the main shut-off valve right away, then call a plumber.
Call one if:
Book plumbing repair with an independent local Pro. In Virginia, plumbing work done for pay needs a DPOR tradesman license, or the supervision of someone who holds one (Va. Code § 54.1-1129, as of September 2026). DPOR is Virginia's Department of Professional and Occupational Regulation. Check a plumber's license for free on DPOR's License Lookup. This is general information, not legal advice; confirm with DPOR.
Your heating system is what keeps the pipes above freezing, so a breakdown in a cold snap puts every pipe in the house at risk. If the heat stops working, book heating repair right away, and open the cabinet doors and let the faucets drip until it's fixed. Anything involving gas lines, gas valves or the furnace's burners is work for a licensed HVAC or gas-fitting professional.
If your water heater sits in an unheated garage or crawl space, ask a plumber before winter how to protect it and its pipes. If it leaks, stops heating or its pipes froze, don't try to fix, drain or relight it yourself. Book water heater repair.
If an outdoor faucet drips, a shut-off valve sticks or you can't find the main, book plumbing repair with an independent local Pro before the first hard freeze.
Last updated September 2026.
It makes them cool faster, but not colder. The National Weather Service says wind chill only shortens the time a water pipe takes to cool, and the pipe "will not cool below the actual air temperature". Drafts blowing on a pipe still matter, which is why sealing gaps helps.
Don't thaw it yourself: call your water utility. Arlington County tells residents not to thaw a water meter. In Loudoun, call Loudoun Water at 571-291-7880, or 571-291-7878 after hours (as of September 2026).
It depends which side of NoVA you're on. NOAA's 1991–2020 normals put the average first 32°F night around October 24 at Dulles and November 18 at Reagan National. Those are 50/50 dates, so in about half of years the first freeze comes sooner.