During extreme heat waves remember to stay hydrated and do not leave children or pets unattended in a locked vehicle. (31264)

LOS ANGELES, Calif. — The Southland’s heat wave went into a second day today, and forecasters said it would last through the weekend.

“In many areas, daytime temperatures will climb 10 to 15 degrees above seasonal normal,” according to a National Weather Service advisory, which noted that today’s warmest spots in Los Angeles County would be the western San Fernando Valley and the Santa Clarita Valley.

Amid muggy conditions, a small chance of showers and thunderstorms is forecast for this afternoon in the San Gabriels in Los Angeles and Ventura counties.

Maximum high temperatures today will top out at between 100 and 105 degrees Fahrenheit but could actually feel even warmer in some places because of the humidity, forecasters said. Overnight temperatures also will be unseasonably high — up to 80 degrees in some communities in the foothills of the San Gabriels.

The Los Angeles County Department of Public health issued a heat alert for the eastern San Gabriel Valley, noting that the high temperatures were expected to continue through the weekend.

“Everyone should remember to take special care of themselves, children, the elderly and their pets,” county public health officer Dr. Jonathan Fielding said. “Extreme heat such as this is not just an inconvenience, it can be dangerous and even deadly.”

The high pressure now parked over the Southland is expected to weaken Saturday and Sunday, but only slightly, according to the NWS advisory. As a result, there could be “slight cooling” in inland areas, but the coastal plain will remain unseasonably warm because of a weak offshore flow expected to develop.

Anyone planning to be outdoors in these conditions “should practice their heat safety,” according to the NWS advisory. “Keep your body hydrated with plenty of water and avoid strenuous activity during the hottest part of the day.”

The NWS forecast highs today of 79 in Newport Beach; 82 in Avalon; 84 at LAX; 85 on Mount Wilson; 94 in downtown L.A.; 97 in Long Beach; 98 in San Gabriel, Palmdale and Lancaster; 100 in Anaheim; 101 in Burbank and Pasadena; 103 in Woodland Hills; and 104 in Saugus.

An extended NWS forecast indicates a cooling trend will start in some areas on Monday, when the high in downtown is expected to be 10 degrees lower than today, but temperatures in the Antelope Valley will dip only on Wednesday — and only slightly.

Los Angeles County has cooling centers available throughout the area. A complete list of the centers is available online at www.publichealth.lacounty.gov or by calling 211.