If you are spending any time outside this summer, chances are you’ll be exposed to a lot of sun, high temperatures and humidity.

Your body is extremely sensitive to its internal temperature. Changes of just one or two degrees can result in several physical functions not working as well as they should. Our brain wants to keep the body at or around 98.6 degrees Fahrenheit, so when we are exposed to extreme heat, two things happen:

• We sweat to cool down, because the process of sweat evaporating off our skin has a cooling effect.
• We pump blood to the skin’s surface and into our extremities to allow all the internal heat carried by our blood to escape. This is why we often appear flushed when it’s hot outside.

These physical responses are hard on the body and can lead to heat-related illness.

When does heat exhaustion become heatstroke?

Heat exhaustion: how to recognize the signs

Sweating is your body’s natural, built-in cooling system. Healthy people who aren’t used to heat can sweat more than six cups of liquid in an hour on a super-hot day.⁴ That’s according to a report from the Institute of Medicine.

Heat exhaustion can happen when you lose too much water and salt. That makes your body overheat and struggle to cool down. You’ll start to notice symptoms like these⁵:

• heavy sweating
• cold, pale and clammy skin
• fast, weak pulse
• nausea or vomiting
• muscle cramps
• tiredness or weakness
• dizziness
• headache
• fainting

How to prevent heat exhaustion and heat stroke

On very hot, humid days, try to stay in an air-conditioned space and cancel outdoor events, if possible. If that’s not an option, here are some tips for preventing heat stroke and heat exhaustion:

50. Drink plenty of water. Thirst is one of the first signs that you’re becoming dehydrated, so don’t wait until you’re thirsty to drink water. Staying hydrated is important year-round, but especially on hot summer days. Overall, you should aim for at least 6-8 glasses of water every day – or more when you exercise.
50. Avoid strenuous activity. While it may be possible to do lighter forms of exercise, like walking or cycling, if you’re taking steps to do them safely, avoid doing anything that puts a large amount of strain on your body – such as heavy weightlifting.
50. Apply sunscreen and stay in the shade. Reapply sunscreen every two hours, especially if you’re swimming or sweating, even when you’re in the shade. You should also opt for wide-brimmed hats, sunglasses with UV protection and other protective clothing on sunny days. Try to stay in shaded areas when the sun is at its strongest – usually between 10 a.m. and 4 p.m.
50. Wear appropriate clothing. Choose clothing that is made of thinner, lighter materials, like linen or cotton, to help your body stay cool. If you know you’ll be spending time in the sun without access to shade, make sure to wear a wide-brimmed hat and UV protective clothing that covers your arms and legs.
50. Cool off at night. Cooler nighttime temperatures give your body a chance to recover, but sometimes the day’s heat carries over into the night.  Without air- conditioning, it can be hard to sleep when it’s hot. Before going to bed, take a cool shower, put a sheet in the freezer or set up fans around your bedroom to make sure you stay cool through the night and can be ready to take on another hot day.
50. Know the signs and symptoms. Being aware of the symptoms of heat exhaustion and heat stroke can help you and others stay safe.