Buckle up, folks. Philly heads into the hottest weekend of the year Saturday, with the heat index possibly hitting 115 degrees, according to the National Weather Service. The city declared a “heat health emergency” through Monday, which means that cooling centers and community pools will hold special hours for people who need a reprieve.

Here’s everything you need to know about how to stay cool this weekend.

What is a cooling center — and how cool will it be?

To keep people cool en masse, the city turns to a go-to resource it already has: the library.

“We try to keep them between 74 and 76 degrees,” says Lynn Williamson, chief of neighborhood library services for the Free Library of Philadelphia.

This year, 12 branches are participating, including the Joseph E. Coleman Northwest Regional Library and Widener Library. You can find a full list at freelibrary.org. In most cases, their Friday hours extend from 10 a.m. to 8 p.m. (Some will close at 7 p.m. The Free Library will update its blog with any changes to hours.)

“You can browse the internet and flip through magazines," Williamson says. “At some locations, staff may also bring out board games.”

In most cases, the libraries will operate as usual. Some will open meeting rooms for people to eat in. (The library only allows covered nonalcoholic beverages outside meeting rooms.) But you don’t have to worry about staying quiet.

“You can have conversations, that’s definitely what we want to see,” she says. “Everyone is welcome.”

How can I get to a cooling center?

Lyft will provide free rides to cooling centers this weekend. Use the code PHICOOL19 to receive two rides, up to $15 each, from now until July 21 at 11:59 p.m.

I’ll get stir-crazy sitting inside all day. What can I do?

Head to one of the city’s 60-plus public pools and spraygrounds (think of a smaller version of Dilworth Park’s massive concrete sprinkler system, built into your local playground). Check the city’s online map to see what’s close to you. Pools are open noon to 5 p.m. on weekends and 11 a.m. to 7 p.m. during the week and will operate on a free swim schedule until further notice.

“That means that there’s no set program for little kids or adults, so anyone can hop into the pool and cool off,” says James Garrow, the director of communications at the Department of Public Health.

Because the number of people allowed in the pool at once is determined by how many lifeguards are on duty, Philadelphia Parks and Recreation is upping staff for the weekend, according to spokesperson Maita Soukup.

Will swimming when it’s this hot out really cool me off?

According to physicians, it will.

“One of the ways the body thermoregulates is through conduction, which is transferring heat from the body to a cooler surface that it’s in contact with,” says Aditi Chincholi, a primary care physician at Mercy Health Associates at Chestnut Street. “Swimming would transfer excess body heat to the water in the pool, which will help regulate body temperature and keep it within normal body limits.”

Water in outdoor pools is typically cool and circulated, so even when it’s sunny and scorching out, a pool that’s at body temperature or below will help keep you cool.

“Don’t forget to stay well hydrated and drink electrolytes and cool water,” Chincholi says. “Make sure you’re wearing loose clothes and sunscreen if you’re going to be out in the sun.

How else can I stay cool during this heat wave?

Staying cool during the heat wave is important for everyone, especially kids — they’re much more vulnerable to excessive heat. The city encourages everyone to wear light colors, avoid drinking alcohol, stay in air-conditioned spaces, and check up on relatives and friends to make sure fans and air conditioners are working.