Santa Rosa is opening a cooling center at the Finley Community Center Sunday amid a scorching heat wave that has prompted health warnings and already broken local records.

The city on Saturday hit a peak temperature of 100, setting a new high mark, with even hotter weather forecast Sunday as the mercury is set to climb above triple digits across the North Bay, marking an early blast of summer that has people seeking relief on the coast, at pools and indoors.

On Saturday, Santa Rosa’s Ridgway Swim Center had reached its capacity of 381 by mid-afternoon, according to a city employee. The Finley Aquatic Center also was bustling.

“It’s very busy,” the employee said.

The National Weather Service has put a heat advisory into effect from 11 a.m. Sunday to 11 p.m. Monday.

Officials warn that the combination of high temperatures and humidity increase the risk of heat-related illness.

It’s an abrupt change from about a week ago, when thunderstorms and cool temperatures had many in the North Bay bundling up to stay dry.

“The concern is that people haven’t had that opportunity to acclimate to the significant heat increases,” Assistant Santa Rosa Fire Marshal Paul Lowenthal said.

“That’s why we really want people to heed the cautions and don’t overdo it this weekend.”

Experts recommend drinking lots of fluids while avoiding sugary or alcoholic drinks; staying where it’s cool or air conditioned; avoiding exertion in the heat and wearing lightweight, light-colored clothes.

The health risks of extreme heat include heat rash or cramps, heat exhaustion and heat stroke, which occurs when a person cannot sweat sufficiently to regulate his or her body temperature for any number of reasons, potentially causing permanent brain or organ damage, or even death.

Particularly vulnerable are babies and children up to age 4, the elderly, those who are obese or disabled, and anyone who works or exercises outside, according to the Centers for Disease Control.

Sunday’s cooling center at Finley will be open from 11 a.m. to 7 p.m. Water will be provided.

No animals other than service animals are permitted inside, officials said.

The heat wave is expected to last through Thursday. PG&E reported that would be the longest period of excessively hot weather in its service area since 2013.

The utility suggested people keep flashlights, batteries and radios on hand in case of power outages.

The city of Santa Rosa is advising residents they can seek relief this week in an air-conditioned lobby of a Recreation and Parks Department building. Locations include:

Finley Recreation Complex at 2060 West College Ave.

Steele Lane Community Center at 415 Steele Lane.

Person Senior Wing at 2060 West College Ave.

You can reach Staff Writer Derek Moore at 707-521-5336 or derek.moore@pressdemocrat.com. On Twitter @deadlinederek.

Four unauthorized occupants were arrested for burglary and conspiracy in Anderson Valley vacation home.