Surviving the Freeze: Preparing Your Furnace for Will County’s 2025 Winter

As we turn the calendar to 2025, Will County residents know the drill: the holiday lights go up, and the temperatures drop. In Northern Illinois, this year polar plunges and biting winds that test the limits of our homes, as well as higher than normal snowfalls are predicted.

As we approach this coldest stretch of winter, it is the perfect time to discuss the added stress sub-zero temperatures place on your heating system. The colder it gets outside—whether you are in Frankfort, Tinley Park, Bolingbrook, or Glen Ellyn—the harder your furnace has to work. This increased workload can lead to faster wear and tear and, unfortunately, reduced indoor comfort just when you need it most.

Here is what you need to know to keep your home warm and your furnace running smoothly during the predicted winter weather.

Understanding "Design Temperature" in Northern Illinois

Before we dive into tips, it is helpful to understand how heating systems in our region are engineered.

follows specific climatic design standards as well. In the Chicagoland area, residential heating systems are typically sized based on a 99% design temperature—usually around -4°F to -10°F.

What does this mean for you? Basically, your furnace is sized to maintain an indoor temperature of 70°F when it is roughly -5°F outside.

• The Reality Check: When Mother Nature throws us a curveball and temperatures drop well below -10°F (hello, Polar Vortex), your system is operating beyond its design capacity.
• The Result: Your furnace might run continuously and still struggle to hold that 70°F mark. This doesn't necessarily mean it’s broken; it means it is fighting a battle against extreme physics.

4 Tips to Protect Your Furnace During Sub-Zero Temps

To help your system keep up with the 2025 winter chill, try these strategies to reduce strain and maintain comfort.

1. Ditch the "Setback" Schedule

Modern smart thermostats are great for saving money by lowering the heat while you are at work or sleeping. However, during a severe cold snap, this strategy backfires.

• The Scenario: You normally drop the heat to 66°F while at work and ask the furnace to bring it back to 70°F when you return.
• The Problem: When it is below zero outside, your furnace is already running at max capacity just to maintain temperature. Asking it to recover 4 degrees is like asking a runner to sprint uphill after a marathon. It puts immense stress on the heat exchanger and blower.
• The Fix: During extreme cold warnings, set your thermostat to a "Permanent Hold" (e.g., keep it at 70°F constantly). Consistency is key to survival.

2. Check Your Filter Before the Cold Front Hits

This is the simplest way to prevent a breakdown. Your HVAC system needs to breathe to work.

• If your filter is clogged with dust and debris, it restricts airflow.
• Restricted airflow forces the blower motor to work harder and can cause the furnace to overheat and shut down on a safety limit switch.
• Check your filter today. If it’s grey or fuzzy, replace it immediately to ensure maximum airflow during the heavy workload ahead.

3. Leverage Passive Solar Gains and Utilize Window Coverings

You can give your furnace a break by using the sun—but be strategic about it.

• Sunny Days: Open the drapes on south-facing windows. Even in freezing temps, the sun can naturally raise your indoor temperature by several degrees.
• Gray/Windy Days & Nights: If it is overcast or dark, keep those drapes shut tight. They act as an extra layer of insulation against the glass, which is the coldest part of your wall.

4. Stop the Drafts

In Will County, the wind chill is often the real enemy. A poorly sealed exterior door can leak as much heat as a hole in your wall.

• The "Snake" Method: If you feel a breeze at the bottom of your door, use a "door snake" or draft blocker.
• The Quick Fix: In a pinch, roll up a heavy towel or blanket and push it against the threshold.
• Don't Forget the Garage: If you have an attached garage, keep that overhead door closed. An open garage door sucks heat right out of the adjacent rooms.