6 ways to prepare for a heat wave — how to stay safe and healthy in high temperatures

• To prepare for a heat wave, you should know how to prevent heat exhaustion and heatstroke.
• If you have air conditioning, make sure it's clean and working properly ahead of extreme heat.

A heat wave is a period of unusually hot weather that lasts for two days or more, often combined with excessive humidity.

Extreme heat can be dangerous. In the US, over 650 people die each year from preventable heat-related illnesses, according to the Centers for Disease Control and Prevention (CDC).

To prevent these heat-related illnesses — like heatstroke — from occurring, there are a number of steps you can take as a heat wave approaches. Here's what you can do in your home to stay cool and prepare for a heat wave.

1. Check your air conditioning

The best protection against heat-related illness is air conditioning, according to the CDC.

If your home is air-conditioned, you can get the most out of it by making sure the unit is working properly before the weather heats up. You can hire an HVAC professional to maintain it each year, or do it yourself. Be sure to turn off the unit before checking it.

Here's what to do:

• Replace the filters if they're dirty. Clean filters can lower an AC unit's consumption of energy by up to 15%, according to the US Department of Energy (DOE).
• Check for clogs. Insert a stiff wire into the drain channel to check for clogs that could prevent the air conditioner from lowering humidity. This plastic or metal tubing, often located next to the indoor unit, collects condensation and drains it outdoors.
• Vacuum the registers to remove any dust. If you have central AC, these are the plastic or metal grills that cover the air ducts in the walls, ceilings, or floors.

Note: The placement of these air-conditioner components can vary among manufacturers, so refer to your owner's guide to locate them.

2. Stay cool without air conditioning

If you don't have air conditioning, you can help keep your home cool by doing the following:

• Turn on ceiling fans and portable fans while you're in a room. You should turn them off when you leave the room or if no one else is in the room to feel the airflow.
• Make sure the ceiling fan is turning counterclockwise as you look up at it so it moves cooler air down instead of upward.
• However, if the temperature is above 90 degrees, the National Weather Service warns that you shouldn't let the air from fans blow directly toward you because it can quickly dehydrate you.
• The Department of Homeland Security (DHS) doesn't recommend using electric fans if the temperature outdoors is above 95 degrees, because while you may feel cooler from the moving air, it won't lower your body temperature, which could result in a heat-related illness.

3. Cover windows that get sun

To prevent the sun from heating your home, you should keep blinds and other window coverings closed during the day. About 76% of the sunlight that passes through double-paned windows becomes heat, according to the DOE. Shades can help lower that heat by up to 20 degrees.

The best type of window coverings to keep your home cool, the DOE says, are insulated cellular shades. That's because their air pockets help provide insulation against the heat from the sun.

To help deflect heat away from your home, the DHS also suggests covering your windows with a reflector, such as cardboard covered with aluminum foil.

4. Keep water stocked in the fridge

It's important to stay hydrated during a heat wave. Drinking water helps replace the fluids you lose through sweating, which is your body's way of keeping you cool as the perspiration evaporates on your skin.

Drinking refrigerated water may have the double benefit of providing hydration while cooling you off. One small study of 45 physically fit men found that drinking cold water during a workout reduced their body temperature significantly more than drinking room-temperature water.

If you're planning on being active during a heat wave, it's especially important to drink lots of water to help make up for the loss of fluid through sweating. And, for everyone, it's necessary to start drinking water even before you feel thirsty.

"If you reach that point, you've probably already lost too much fluid from your body," says Mark Conroy, M.D., an emergency medicine physician at The Ohio State University Wexner Medical Center.

It's also important to limit alcohol during a heat wave. Alcohol can dehydrate you, as it's a diuretic that causes your body to quickly lose fluids through your urine. Alcohol also interferes with your body's ability to lose heat.

5. Plan to eat cool foods

It's best to eat a lot of fruits and vegetables during a heat wave, Conroy says. For example, watermelon, lettuce, and cucumbers are over 90% water, which will help keep you hydrated.

The American Red Cross recommends that you eat small meals throughout the day. You should avoid meat and high-protein foods because they can increase your body's production of heat.

To avoid adding more heat to your home, you should use the microwave or an outside grill instead of the oven.

If you must use the oven, turn on the vent fan to send the hot air outside. Instead of repeatedly opening the oven door to check on what you're cooking, turn on the oven light and look through the glass. This will limit the oven from heating up your home.

6. Know how to stay safe during a heat wave

Overall, staying inside your air-conditioned home is the safest place to be during a heat wave.

This is especially true for children under age four, and older people over age 65, as they are at a higher risk for heat-related illness.

But, if you must go outside, here are some additional ways to stay safe and comfortable when the temperature rises:

• Wear loose-fitting, light-colored, and lightweight cotton or moisture-wicking clothing to help keep cool.
• If you want to exercise outdoors, do it early in the morning or an hour before sunset — avoid strenuous activity between 11 a.m. and 4 p.m., when temperatures are highest.
• Take a cool shower or bath. You can also place ice packs on your head and armpits to help lower your temperature.
• Never leave children or pets in a parked car, even with the windows cracked open. The temperature inside can rise to a dangerous level within just a few minutes.

During a heat wave, it's also imperative to know the symptoms of heat-related illness. Heat exhaustion can quickly progress into heatstroke, which may cause organ damage or death if medical attention isn't received immediately.

If you experience the symptoms of heat exhaustion, you should cool yourself down immediately by resting in shade, air conditioning, and utilizing cold water. And if heatstroke symptoms develop, you should call 911 immediately.