The first stretch of 90 degree days always seems to arrive before anyone is ready. A little prep in late spring is the difference between a home that stays cool from day one and a scramble to find a working fan during the first heat wave. None of it is complicated, and most of it is cheap or free.
Getting ready for summer heat comes down to a few things: make sure your cooling actually works and is sized for the space, stop sun and hot air from getting in, keep humidity in check, and clean up the air that has been trapped inside all winter. Here is a simple checklist, followed by the details that matter for each step.
Your summer readiness checklist
Work down this list once each spring. The whole thing takes an afternoon and pays off every hot day after.
| Task | Why it matters | Best time |
|---|---|---|
| Test or service the AC | Confirms it cools before the first heat wave and catches a dirty coil or low refrigerant early | Late spring |
| Clean or replace filters | A clogged filter chokes airflow and drives up energy use | Monthly in season |
| Seal windows and doors | Stops cool air escaping and hot air leaking in | Before it gets hot |
| Add or adjust window coverings | Blocking direct sun cuts the solar heat that loads up a room | Before peak sun |
| Set up fans | Moving air lets you raise the thermostat and stay just as comfortable | Anytime |
| Manage humidity | Damp air feels hotter and invites mold and dust mites | Before humid months |
| Freshen indoor air | Pollen, dust, and cooking smoke build up while the windows stay shut | Start of season |
Cool the rooms you actually use
You do not need to cool the whole house to the same temperature. Focus on the rooms you spend time in and match the cooling to each space rather than overspending on one oversized unit.
- Window air conditioners give the most cooling per dollar for a single room. Size them to the room before you buy, since an oversized unit short-cycles and leaves the air cold and clammy.
- Portable air conditioners roll room to room and work where a window mount is not allowed, such as a rental with a strict lease.
- Mini-split systems deliver quiet, efficient cooling for a larger area, a multi-room zone, or a whole floor.
- Fans are the cheapest comfort upgrade there is. Moving air lets you set the thermostat a few degrees higher and feel the same.
Get ahead of humidity, it feels hotter than the thermostat says
Muggy air is the reason a room can feel hotter than the number on the thermostat. Sweat cannot evaporate off your skin, so the same temperature feels heavier and warmer. The chart below uses the National Weather Service heat index to show how much humidity changes the way an 85 degree room feels.
Keeping indoor humidity between 30 and 50 percent, the range the EPA recommends, makes rooms feel cooler and discourages mold and dust mites. A dehumidifier handles damp basements and humid climates, and your air conditioner pulls moisture out of the air as it runs, which is one more reason to size the AC correctly instead of oversizing it.
Clean the air that has been shut in all winter
Once the windows close and the AC takes over, the same indoor air circulates for months. Pollen, pet dander, dust, and cooking smoke build up with nowhere to go. A portable air purifier with a true HEPA filter clears the fine particles you cannot see. Match it to your room using its AHAM Clean Air Delivery Rate, or CADR, which tells you how much air it actually cleans per minute rather than just how big a room the box claims. An ENERGY STAR model keeps the running cost down since a purifier often runs around the clock.
Set the thermostat for comfort and lower bills
The Department of Energy suggests around 78 degrees when you are home in summer, and a few degrees higher when you are out or asleep. Every degree you can raise the setting trims your cooling bill. This is where fans earn their keep. With air moving across your skin, most people stay comfortable a few degrees warmer, so you capture the savings without feeling the difference. A programmable or smart thermostat makes the swing automatic, easing the setting back down before you get home so the house is ready when you walk in.
