This summer, a lot of us are going to spend hours at a time out in the heat. If you’ve never been struck by heat exhaustion before, it doesn’t mean you won’t this year. In fact, did you know annually there are more than 600 people killed by extreme heat in the United States – it’s true.

Considering these are preventable deaths, you can avoid a trip to the emergency room by knowing some of the heat exhaustion signs and symptoms.

1. Thirst

There are two types of heat exhaustion – one based off salt and one based off water. Any headaches, weakness, loss of consciousness, or excessive thirst is usually related to the body depleting itself of water. Dark-colored urine is a possible warning sign of dehydration related to heat. If you’re noticing your urine to be particularly colorful, it’s a sign you need water and potentially are at risk of heat exhaustion.

2. Heavy sweating

Heat exhaustion happens when the body can’t cool itself down like it normally could. When there’s so much heat that it overpowers our natural systems, it can send sweating into overdrive trying to compensate.

If you’re experiencing more sweating than you normally would or have been in the heat for an extended period of time sweating throughout, you could be at risk. Subsequently, when someone reaches the stage of going into heatstroke, they’ll notice moving from sweating into feeling dry. You may be able to prevent these heat exhaustion signs and symptoms by wearing the appropriate personal air cooling clothing.

3. Dizziness

Heavy heat is known to cause a response from our circulation system including seeing more blood flow to the skin as well as the pooling of blood in the lower extremities. As the blood rushes to regions like these, it can cause blood pressure to drop which in turn results in light-headedness. Left untreated, this can quickly manifest into heatstroke.

4. Headache

Headaches associated with heat are not actually from the heat itself but rather being dehydrated. When we become dehydrated, it’s our body’s natural response to develop a throbbing headache. Fortunately, all that’s required to combat a headache is hydration which, assuming one does as a precautionary measure, can set themselves up for no headache at all.

5. Weakness

It’s normal to feel weak in the face of heat exhaustion. This weakness is from our body working its hardest to stay cool and to make use of the depleting hydration it has to keep things running smoothly. If you’re feeling sudden weakness, move to a cooler place, grab a cool cloth, get water, or jump in a cool bath. It could be a sign you’re about to faint or could be a hint that something serious is about to happen.

6. Fainting

Fainting from heat exhaustion is the direct result of reduced blood flow to the brain, caused by peripheral vessel dilation. This is when in a heated environment, blood pressure lowers and the body dilates its small blood vessels to radiate heat. Then, when someone stands up quickly or is standing for a long period of time, the risk of fainting spikes under the summer sun.

7. A weak pulse

A weak but faster pulse can be a sign that the body’s working hard and failing to keep up with the heat around it. This is a major sign of heat exhaustion and if left untreated, will lead to heatstroke and medical attention will need to be sought. Symptoms like a weak pulse can worsen quickly.

8. Cramps

Cramps can be very painful when they originate from heat exposure and exhaustion. These sort of cramps are generally brief and occur during or after strenuous activity in the heat. Muscles typically will spasm or jerk involuntarily, which is caused by a deficiency in electrolytes. This only highlights the importance of replenishing electrolytes when in the heat.

9. Cold or pale skin

Cold, pale, or damp skin sometimes accompanied by goose-bumps is a sign of heat exhaustion which shouldn’t be discounted. This can be a sign the body is going into shock and/or a person experiencing heat exhaustion is about to pass out.

10. Vomiting

The body’s always going to react when it’s experiencing heat exhaustion and sometimes how it reacts is by vomiting. Any feeling of nausea or vomiting is a sign a person needs to get out from the heat and into a cool environment. Considering vomiting is a sign a person could be getting closer to heatstroke, there are risks to the brain, heart, kidneys, and muscles, and even fatal consequences which need to be remembered.

11. Loss of consciousness

If someone experiences a loss of consciousness, it could be a sign they’ve moved from heat exhaustion into heatstroke. Heatstroke can occur as the body temperature rises above 103 degrees, the pulse increases, and a variety of the symptoms on this list begin to present themselves. Loss of consciousness is an immediate sign that a 911 call is needed and that a person needs to be moved out from the sun or heat.