The City of Philadelphia declared the first heat emergency of the year, which began at 8 a.m. Thursday and will last until Saturday midnight.

Several protocols have been activated due to the emergency, with the water department suspending utility shutoffs and the Office of Homeless Services declaring a Code Red for unhoused residents.

MORE: Here’s how to protect phones, laptops and cars from damage in extreme heat

There are 153 cooling centers and sites open to the public in Philly, including Free Library locations, recreation centers, senior centers, schools, spraygrounds and pools.

Philadelphia’s Animal Care & Control Team enforce additional pet safety measures, with dogs required to have at least one area of shade to accommodate the entire body. Violators of the ACCT Philly policy will result in a fine of $500 or more.

When does Philadelphia declare heat emergencies?

The city’s Health Department declares a Heat Health Emergency when the forecasted heat index, which is what the temperature feels like to the human body taking humidity and air temperature into account, is in a certain range for a certain number of days.

From May 1 to June 30,  that’s two consecutive days of a heat index from 101 to 105 heat index or three or more days of a heat index from 98 to 102. From July 1 to Sept. 30, it’s two consecutive days of a heat index above 106 or three or more days of above 103.

The National Weather Service declared a heat advisory until Saturday at 6 a.m. and an excessive heat watch from Saturday morning to Sunday evening in Philadelphia and surrounding counties. The heat index may reach 99 during the heat advisory and can get as high as 106 during the excessive heat watch.

Who is at risk for heat stress?

Signs of heat stress include decreased energy, slight loss of appetite, faintness, lightheadedness and nausea.

Those most at risk from heat-related health conditions are older adults, people without air conditioning, individuals with chronic medical conditions, pregnant women, small children, those who work in high-heat environments, those who take medications that affect body temperature, alcohol and drug users and people engaged in strenuous physical activity.

Anyone concerned with detecting signs of heat stress can call the Philadelphia Corporation for Aging (PCA) Heatline at (215) 765-9040 to speak to a city Health Department nurse to ask questions.

How to avoid heat-related illness

City officials recommend that those at risk use air conditioners or fans, or visit a location with air conditioning. Drink plenty of water to avoid dehydration, and avoid alcohol and caffeine. Do not leave children, older people or pets alone in cars.

Wear lightweight and light-colored clothing, and remove any excessive clothing. Cover exposed skin with SPF sunscreen and consider wearing a wide-brimmed hat to protect the face and head.

Be sure to maintain a normal diet and consult a doctor if you regularly take medications, as the heat can cause some medications to have an adverse effect. Avoid outdoor activities if possible, especially during the sun’s peak hours of 11 a.m. to 4 p.m., and shower or bathe in water that is close to skin temperature.