Philly’s getting a heat wave. Here’s what to know about symptoms and treatment for dehydration and heat exhaustion.

A heat wave is expected to raise temperatures near 100 degrees in the coming days. If needed, the city can declare a heat emergency and open centers where people can go to cool off, among other measures.

Staying healthy during the heat wave comes down to two basic things: drinking water and cooling down as much as possible.

Here is what you need to know about heat-related illnesses:

Water serves critical functions in the body, including cooling it down, maintaining blood volume, and balancing electrolytes.

Dehydration happens when individuals lose more water than they are taking in. Even though it could happen to anyone, dehydration poses a specific risk to children, elderly, and people with chronic illnesses.

The signs of dehydration are dark-colored urine, less frequent urination, fatigue, confusion, and dizziness. With babies, parents should monitor diapers to ensure that they are continuing to provide urine.

Untreated dehydration can contribute to heat exhaustion or heatstroke, reduced blood pressure, fainting, and seizures.

As the body remains overheated, it will continue to sweat and further lose liquids. If individuals’ skin becomes cold and pale, they complain of dizziness and headaches, and seem tired or weak, these are all signs they might be suffering from heat exhaustion.

At this stage, consider calling 911 if a person is vomiting, the symptoms get worse, or last longer than one hour.

» READ MORE: How to avoid heatstroke and heat exhaustion

Heatstroke is when the body can no longer regulate its temperature. People may stop sweating and spike a fever. The cold, pale skin could turn hot and red. In addition to the fever, people may be confused, pass out, and vomit.

If someone is vomiting, unable to drink, or losing consciousness, medical attention is likely needed in an emergency department. Medical staff there can cool the person down and provide intravenous fluids. If you suspect that someone is suffering heatstroke, call 911.

Water is your best friend during the heat wave. As much as possible, keep hydrated. Adequate water intake for adults is about 11 to 15 cups a day. While water is not the only hydrating drink, avoid caffeinated and alcoholic drinks, which can contribute to dehydration.

Cooling down is also critical. Look for shade, avoid the sun, and when possible, stay inside air-conditioned buildings. This will help the body regulate heat and preserve liquid, especially during the hottest hours of the day in the afternoon.

There are open splash parks and pools throughout the city where people can go to cool down, though if you spend time in the sun, be sure to put on sunscreen to avoid sunburns.

» READ MORE: 25 Philly pools will open next week, more to open on a rolling basis

For people who are dehydrated, get them to a shaded and cooler area and have them drink water. If at any point they lose consciousness, vomit, or are unable to drink, seek medical attention immediately.

Two other potential unpleasant outcomes of heat are rashes and cramps.

When sweat is trapped in the skin, a potentially itchy heat rash can appear. It can be in the form of small blisters to larger lumps. Heat rashes usually resolve without treatment when the body cools down. The CDC recommends keeping the rash dry and using baby powder to soothe itchiness. Go see a health-care provider if the rash doesn’t go away within a few days, gets worse, or if you develop additional symptoms or are concerned that other health issues are involved.

Heat cramps are involuntary muscle spasms that can occur due to fluid and electrolyte loss, which is common when exercising on a hot day. If you have heat cramps, stop any physical activity, move to a cool place, and drink water. A sports drink with electrolytes can also help.

Seek medical attention if the heat cramps last longer than an hour or if you have a heart condition.