How to Keep Your Home Cool During a Minnesota Heat Wave
Minnesota doesn’t do gradual. One week it’s a comfortable 75 degrees and the next you’re staring at a forecast showing four straight days in the low 90s with humidity. When that happens, your AC system goes from a convenience to the only thing standing between you and a genuinely miserable week.
Most systems are designed to maintain about a 20-degree differential from outdoor temperature. When it’s 95°F outside, that means 75°F inside on a good day — assuming the system is in good shape, properly maintained, and not fighting a bunch of other problems at the same time.
Here’s how to help your system do its job when the heat pushes it to the limit.
Close the House Early
The single most effective thing you can do during a heat wave is close everything up before the day gets hot. If the overnight low is in the 60s, that cool air is your asset — capture it by opening windows in the evening and closing them early the next morning, before outdoor temperatures pass indoor temperatures.
Once warm air gets into the house, your AC has to work to remove it. If you wait until it’s already 80°F inside to close up, you’ve given the heat a head start.
Blinds and curtains matter too. South and west-facing windows take direct sun in the afternoon, and that radiant heat adds real load to the system. Closing blinds on those exposures during peak sun hours can drop the indoor temperature meaningfully.
Don’t Crank the Thermostat Down
It’s tempting, when it’s hot, to set the thermostat at 68°F and will the house into comfort. But your AC system delivers cool air at the same rate regardless of where the thermostat is set. Setting it lower doesn’t make the system work faster — it just means it runs longer, which increases the chance of it overheating or struggling.
More practically: if you’re asking a standard system to hit 68°F when it’s 95°F outside, you’re asking for a 27-degree differential. Most residential systems aren’t sized for that. The system will run continuously, never satisfy the setpoint, and you’ll wear out components faster.
Set a realistic target — 74 or 75°F — and let the system run efficiently to get there. That’s a better outcome than punishing the equipment chasing an impossible number.
Change the Filter — Especially Before a Heat Wave
A clogged air filter is one of the most common causes of AC performance problems during extreme heat, and it’s also the easiest to fix.
When the filter is dirty, airflow through the system is restricted. That makes the evaporator coil run colder than designed, which can cause it to ice over. When a coil ices up, the system can’t move cool air at all — you’ll notice warm air blowing from the vents despite the unit running. The system often has to be shut off and allowed to thaw before it works again.
During a heat wave, that’s a bad situation. Check your filter at the start of summer and replace it if it’s been more than 60-90 days or looks dirty. This is a $10-15 fix that protects a $5,000 system.
Keep Heat Sources Inside to a Minimum
Cooking on the stovetop or in the oven dumps a significant amount of heat directly into the house. So do clothes dryers, dishwashers running with a heated dry cycle, and even large numbers of lights if you have older incandescent bulbs.
During a heat wave, shift heat-generating tasks to early morning or evening when outdoor temperatures are lower. Grill outside. Run the dishwasher overnight. Use a microwave instead of the oven. These habits don’t sound dramatic but they reduce the load your AC has to overcome.
Give the Outdoor Unit Room to Breathe
Your AC’s outdoor condenser unit dumps the heat it pulls from your house into the outside air. For it to do that efficiently, it needs airflow around the unit. If it’s buried in overgrown shrubs, surrounded by a fence with no clearance, or caked in cottonwood debris from spring, it’s working harder than it has to.
Check the unit at the start of each cooling season. Clear vegetation to at least 18 inches on all sides, straighten any bent fins if they’ve taken damage, and gently rinse the coil with a garden hose if it’s visibly dirty. Don’t use a pressure washer — the fins are delicate. For a full professional clean and inspection, AC maintenance covers all of this and more.
Also check that nothing is blocking the return air vents inside. Furniture pushed against a return vent, or a vent that’s been closed off in an unused room, restricts system airflow the same way a dirty filter does.
Know When to Call
If your system is running continuously and the house is still climbing, that’s not always a sign that the system is failing — it may just be that conditions are at or beyond design limits. But if you’re noticing any of the following during a heat wave, it’s worth a call:
- Warm air from the vents despite the compressor running
- Ice visible on the refrigerant lines outside
- The system cycles off after short run times
- Unusual noises from the indoor or outdoor unit
- A noticeable refrigerant smell (slightly sweet, chemical)
These are symptoms of real problems, not just heat stress, and they won’t fix themselves. Running a compromised system hard during a heat wave is how small problems become expensive ones. If it becomes urgent, emergency AC repair is available.
The Honest Answer
The best time to prepare for a heat wave is before it arrives. A system that’s been tuned up, has clean coils and a fresh filter, and has been checked for refrigerant charge will outperform a neglected one every time — and that performance gap is most obvious exactly when you need it most.
If your AC struggled last summer or you haven’t had it serviced in a couple of years, schedule an AC tune-up before the Brainerd Lakes Area hits its July heat. You’ll be glad you did. If the system is struggling under real heat-wave conditions, see our post on signs your AC is about to break down to know when to call.
Mavericks Heating and Air serves Brainerd, Baxter, Crosslake, Nisswa, Pequot Lakes, and the surrounding area. Call us at (218) 316-0550 or reach out online to get scheduled.