Cold Snap Ready: Preventing Frozen Pipes and Furnace Failures in Chicago Winters

Extreme cold is when Chicago homes are most likely to face two problems at once: a furnace that cannot keep up—or quits entirely—and water pipes that freeze and burst. Both are largely preventable. The keys are keeping your heating system reliable, protecting vulnerable pipes, and knowing your first moves if the heat goes out during a polar vortex.

Why do cold snaps cause furnace failures?

During a deep freeze your furnace may run almost continuously, and that sustained load is what pushes marginal parts over the edge. The most common cold-weather culprits are a clogged filter that restricts airflow and triggers a safety shutdown, a frozen condensate line on a high-efficiency furnace, and an exhaust or intake vent buried by snow. A furnace that coasted through mild weather can stall the first night it truly has to work.

How to prepare your furnace for extreme cold

• Start the season with a fresh air filter and check it monthly.

• Book a fall tune-up so worn parts are caught before the load hits.

• Keep exterior PVC intake and exhaust vents clear of snow and ice all winter.

• Know where your furnace filter, power switch, and reset button are.

• Maintain clearance around the unit so it can pull the air it needs.

• Add a smart thermostat with low-temperature alerts so you know early if the heat drops.

How to prevent frozen pipes

Before the cold hits

• Insulate exposed pipes in unheated spaces—basements, crawlspaces, garages, and along exterior walls.

• Seal drafts near pipes where cold air sneaks in.

• Disconnect and drain outdoor hoses and shut off exterior spigots.

• Find your main water shutoff valve now, so you are not hunting for it during an emergency.

During a deep freeze

• Keep the heat at a steady temperature day and night—do not set it back below about 62°F.

• Open cabinet doors under sinks on exterior walls so warm air reaches the pipes.

• Let a pencil-thin trickle of water run from the faucet farthest from your main line.

• Keep garage doors closed, especially if water lines run through the garage.

What to do if your heat goes out in a cold snap

1. Check the thermostat—confirm it is set to heat, the schedule is right, and the batteries are good.

2. Check the air filter; a badly clogged filter can shut the furnace down.

3. Make sure the furnace power switch is on and the breaker has not tripped.

4. Check that the condensate line is not frozen and the exterior vents are not snow-blocked.

5. If you still have no heat, call for emergency service and protect your pipes in the meantime—open cabinets and let faucets trickle.

Never use a stove, oven, or portable generator to heat your home while you wait—that is a serious carbon monoxide hazard. See our furnace and carbon monoxide safety guide.

What to do if a pipe freezes or bursts

If a pipe is frozen but has not burst, open the affected faucet and warm the pipe gently with a hair dryer or towels soaked in warm water—never an open flame. If a pipe bursts, shut off the main water valve immediately to stop the flooding, then call a plumber. Fast action on the main valve is what limits the damage.

Frequently asked questions

At what temperature do pipes freeze?

Pipes are generally at risk once the temperature drops to about 20°F or below, especially in uninsulated areas—and the longer the cold lasts, the higher the risk.

Should I leave a faucet dripping during a cold snap?

For pipes prone to freezing, a slow trickle relieves pressure inside the pipe and helps prevent a burst. It is cheap insurance during a hard freeze.

Why does my furnace keep shutting off in extreme cold?

The usual causes are a clogged filter, a frozen condensate line, or a snow-blocked exhaust vent. If clearing those does not fix it, call for service before the house gets dangerously cold.

What thermostat setting protects pipes during a polar vortex?

Keep it steady at roughly 62–65°F, even overnight. A steady temperature protects your pipes and reduces the strain of big swings on your furnace.

CCC Mechanical keeps Chicago and suburban homes warm through the worst of winter. If your furnace fails in a cold snap, call 630-827-9024 and take steps to protect your pipes while help is on the way.