Chicago faces several days of extremely high temperatures, and residents are urged to take extra precautions.

That means the usual — keep drinking water, don’t stay outside too long and when you do go out, wear sunscreen.

The city operates six cooling centers, and could open additional ones this week.

“Heat will build to dangerous levels Thursday through Saturday,” according to a National Weather Service statement.

High temperatures will reach into the high 90s on all three of those days, and the heat index — the combined effect of heat and humidity — could exceed 105 degrees.

Don’t expect it to get much better when the sun goes down, either — the temperature won’t drop much below 80 degrees.

“Very warm overnight temperatures will offer little relief from the heat and humidity,” according to the weather service.

The need for preparedness is reinforced by memories of Chicago’s 1995 heat wave that killed 793 people, most of them poor and elderly residents living alone.

Much of the blame fell on a defensive Mayor Richard M. Daley, whose City Hall had a heat emergency plan — complete with public advisories, cooling centers, and well-being checks — but failed to execute that plan until bodies started piling up at the morgue.

Every mayor since then has been on guard for the heat.

“I can assure you that we will be ready,” Mayor Lori Lightfoot said Tuesday.

“We will be putting out heat advisories. As a result of what happened that dreadful summer, there’s a lot of new protocols that are in place. And we will be activating them to make sure that we are being as responsive as we can,” the mayor said in a conference call from New York.

But Chicagoans also have to look out for each other, to “make sure that people are checking in on their neighbors, particularly those who are seniors or otherwise infirm,” Lightfoot said.

“This is a time where we have to step up as neighbors and make sure that we’re taking care of each other.”

Call 311 to find a cooling center near you or request a well-being check on someone you fear may be in danger from the heat.

When temperatures climb this high, there is a greater risk of heat exhaustion and even heatstroke, according to the Mayo Clinic.

Symptoms of heat exhaustion include heavy sweating and a rapid pulse.

More serious is heatstroke, which can occur when a person’s body temperature reaches 104 degrees, according to Mayo.

A person with heatstroke may feel hot and dry; untreated, heatstroke can damage the heart, kidneys, and brain.

If you must go out, the Centers for Disease Control and Prevention recommends sunglasses and a wide-brimmed hat. Also, apply sunscreen with a minimum SPF of 15. Put it on 30 minutes before leaving the house, and reapply often. Look for products that say “broad spectrum” or “UVA/UVB protection,” according to the CDC.

The six city cooling centers are open 9 a.m. to 5 p.m., Monday through Friday:

• Englewood Center, 1140 W. 79th St.

• Garfield Center, 10 S. Kedzie Ave.

• King Center, 4314 S. Cottage Grove Ave.

• North Area Center, 845 W. Wilson Ave.

• South Chicago Center, 8650 S. Commercial Ave.

• Trina Davila Center, 4312 W. North Ave.

Other options to cool off: 21 senior centers are open during their regular hours of operation; and city buildings such as police stations, park district buildings, and libraries, also serve as cooling centers during regular hours.

Those who stay home also may need help against the heat.

“The fans have been selling like hot cakes,” said Daniel Kelley, an assistant manager at Gordon’s Ace Hardware, 24 W. Maple St. The store might sell 50 fans in a typical week, but he’s sold 40 in the last two days.