Nearly 2,000 people each year end up in the emergency room for heat-related illness, according to the Arizona Department of Health Services.

One way to avoid heat illness is to make sure you're properly hydrated. Arizona officials recommend drinking at least 2 liters (about 68 ounces) of water a day — and 1 to 2 liters of water an hour if you're outdoors.

They even recommend drinking when you're not thirsty. Thirst is your body's way of telling you you're already mildly dehydrated, but there are many other warning signs.

Click on the diagram to explore what you may feel if you're experiencing mild to severe dehydration.