AC Not Keeping Up in 100-Degree Heat? What’s Normal

When it’s 100 degrees outside, heat enters through windows, walls, and the roof faster, while your AC has to move that heat outdoors into already-hot air. A system that usually reaches your thermostat setting may run nearly continuously during the hottest hours and catch up in the evening.

Keep exterior doors and windows closed, close blinds on sun-facing windows, and make sure supply vents and return grilles aren’t blocked by furniture or rugs. If the air filter is dirty, replace it with the correct size and type for your system; a clogged filter can restrict airflow and make cooling less effective.

Check the product’s listed specifications when evaluating what to try before calling for service.

Pay attention to a sudden change from your AC’s usual performance, especially if it blows warm air, cycles off unexpectedly, leaks water indoors, or leaves some rooms much hotter than others. Turn the system off and contact an HVAC professional if you see ice on the indoor unit or refrigerant lines, rather than letting it continue to run.

Check the product’s listed specifications when evaluating when struggling points to a problem.

Use fans to help you feel cooler, drink water regularly, and choose lightweight, breathable clothing; fans move air but do not lower a room’s temperature, so turn them off when no one is there. Our Stay Cool in Humid Heat – Summer Wardrobe Guide is a digital download focused on clothing tips, breathable fabrics, and outfit planning, and you can explore our guide to what to wear in humid heat for more wardrobe ideas while you manage the heat at home.