Frozen Pipes: Which Pipes in Central PA Homes Freeze First

By Mechanicsburg Reco. Published October 17, 2026. Updated November 7, 2026.

Pipes do not freeze at random, and you do not need to inspect the whole house. Walk it once, find the four or five places where a water line runs through cold space, and protect those. This post is a walk-through for a Central Pennsylvania home.

The rule of thumb from American Red Cross guidance is that pipes can freeze and burst when outdoor temperatures reach 20 degrees or lower. Estimates of how long that takes vary from about three hours for an unprotected pipe to about six for an insulated one. Air temperature is not pipe temperature, so location and wind matter.

What the local numbers say about your risk

We calculated these from NOAA daily records for the Middletown-Harrisburg station, 1991 through 2020. The average January overnight low was 23.0 degrees. The low reached 20 or below on about 28 nights a year and 10 or below on about 5. The coldest reading in the period was -22 on January 21, 1994. The median last spring freeze was April 9 and the median first fall freeze was November 4.

That means roughly November to mid-April is the window, and any single winter has several nights where an exposed pipe is in trouble.

The walk-through: from highest risk to lowest

1. Outdoor hose bibs

A hose left attached traps water right at the cold wall. Disconnect hoses before the first freeze, close the inside shut-off if there is one and drain the faucet. A frost-free faucet still fails if a hose holds water in it.

2. Unheated garage supply lines

Laundry hookups and utility sinks often run through garage walls that nobody heats. If you have a water line there, wrap it and keep the garage door closed on cold nights.

3. Crawlspace and unheated basement pipes

Pipes near foundation vents and the rim joist take the worst of it. Close or cover vents, seal gaps and insulate exposed lines. See crawlspace water damage for what happens when they fail.

4. Pipes in exterior walls

A kitchen or bathroom on an outside wall puts a supply line against cold sheathing. Open the cabinet doors under the sink on cold nights so room air reaches it, and let the faucet drip.

5. Attic and soffit runs

If water lines run through an attic, check that insulation covers them and that nothing blocks warm air from reaching them.

When the cold nights actually fall

Month	Nights at or below 32	Nights at or below 20
October	0.6	0
November	10.5	0.6
December	22.4	4.9
January	25.6	12.2
February	23.2	8.2
March	16.2	2.4
April	2.6	0

Average nights per month, Middletown-Harrisburg, 1991-2020. About 25 of the roughly 28 yearly nights at or below 20 come in December, January and February. November and March bring plenty of freezing nights but few at 20, so a pipe in a decent spot usually survives them. A hose bib or an uninsulated garage line does not need 20 degrees to cause trouble.

Signs a pipe is freezing right now

A faucet that runs as a trickle or stops completely on a cold morning is the classic sign. Frost on an exposed pipe, a bulge in the pipe wall or a pipe that is cold to the touch while its neighbors are not are others. If you see them, open the faucet, add heat to the space and keep an eye on it. A frozen pipe is not a burst pipe yet, and keeping the water moving and warming the space can prevent the split. Do not use a flame, and do not leave a space heater unattended near the pipe.

Older houses have more surprises

Census survey estimates put about a third of Mechanicsburg's housing as built before 1940 and about 63 percent before 1970. Houses of that age often have plumbing added or rerouted over the decades, sometimes along an outside wall that was never meant to carry a water line. A bathroom added in the 1950s is a common example. If you do not know where your lines run, a plumber can trace them, or you can look for cold spots with a hand along the wall on a cold night.

What a freeze does, and when you find out

Ice blocks the pipe and water trapped between the ice and a closed faucet has nowhere to go, so the pipe gives way. The split often shows only when the pipe thaws, which can be hours after the cold ends. A figure often quoted from the Institute for Business and Home Safety is that a crack one-eighth of an inch wide can release more than 250 gallons a day.

If a pipe splits, close the main shut-off and call (223) 245-0005. The first hour matters, and our post on what to do in the first hour covers it. See also frozen and burst pipe cleanup.

Check your own pipes

Use the frozen pipe risk checker with tonight's forecast low, and the winter pipe checklist to protect them before the next cold snap. We work in Mechanicsburg, Shiremanstown, Camp Hill and Carlisle.

Frozen pipe questions