In its forecast discussion Thursday morning, the National Weather Service Hanford described the upcoming heatwave as “relentless and “vicious.”

An Excessive Heat Warning is already in effect. The warning means a prolonged period of dangerously hot temperatures is expected.

A run of afternoon high temperatures reaching 110 degrees — and above — in the Fresno area is ahead. And there’s a possibility that longstanding record highs could fall on Saturday, Sunday, and Monday.

Fresno’s record high for Aug. 15 is 109 degrees, which was set in 1920. The Aug. 16 mark is 110, also set in 1920. The all-time Aug. 17 high of 111 was set in 1892.

Little Overnight Relief

In addition, no significant overnight cooldowns will accompany this heatwave. NWS says overnight lows could be above 80 degrees in some parts of the San Joaquin Valley.

“This high-pressure ridge will not likely budge for many days, so it’s possible that the Excessive Heat Warning might have to be extended into next week,” the NWS said.

Stay Out of the Sun

Health officials are advising residents to guard themselves against heat-related illnesses such as heat exhaustion and heatstroke.

Remember to stay hydrated by drinking plenty of water, and try to limit outdoor activity.

Don’t forget pets. Never leave them in a parked vehicle.

Cooling Centers Open Friday

In Fresno, cooling centers will open Friday and remain open until further notice, City Hall said. The hours are 1 p.m. to 7 p.m. at:

• Ted C. Wills Community Center, 770 N. San Pablo Ave.
• Frank H. Ball Neighborhood Center, 760 Mayor Ave.
• Mosqueda Community Center, 4670 E. Butler Ave.
• Pinedale Community Center, 7170 N. San Pablo Ave.

FAX is providing free bus service along normal routes to and from the cooling centers. To ride free, tell the driver you are going to a cooling center.