How cold does it have to get before pipes freeze?
Bare pipes in a garage, attic or outside wall start to freeze at about 20°F. Pipes inside a heated house hold out far longer. Look up your county to see how many nights a year it normally gets that cold.
3,140 counties. A normal year from NOAA records, not tonight's forecast.
Where is the pipe?
- 32°F Outdoor spigot, open crawlspace 100% of counties get this cold at least one night a year
- 20°F Bare pipe in garage, attic or outside wall 94% of counties get this cold at least one night a year
- 10°F Insulated pipe in unheated space 74% of counties get this cold at least one night a year
- 0°F Inside the heated house 54% of counties get this cold at least one night a year
Thresholds follow University of Illinois Building Research Council guidance, the source behind the Red Cross 20°F rule. Wind on an outside wall makes any of them happen sooner.
If it is tonight
- Open the cabinet doors under sinks on outside walls.
- Let the cold tap on those sinks drip, thin as a pencil lead.
- Keep the heat at 55°F or higher, including rooms you are not using and when you are away.
- Unhook garden hoses. A hose left on traps water in the spigot.
- Find the main shutoff now, while nothing is leaking.
A tap that gives a trickle or nothing in the morning is already frozen. Leave it open, warm the pipe with a hair dryer working back from the tap, and never use an open flame. A thaw call from a plumber is about $100; a burst averages $500 and can pass $3,000.