National Weather Service issues heat advisory

Power demand expected to set another record late today

The National Weather Service in Sacramento has issued a heat advisory for the Northern San Joaquin Valley and Southern Sacramento Valley.

"The combination of a very hot air mass and monsoonal moisture will create very hot and humid conditions through Saturday evening," the Weather Service says in the advisory. "Places that are most impacted by this advisory are inland locations away from any Delta influence."

The advisory is in effect until 9 p.m. Saturday.

A heat advisory means the daytime heat index will be 105 degrees or higher and the nighttime index will be 80 degrees or higher for two consecutive days. The heat index is the measure of the effect of combined temperature and humidity on the body.

Places close to the Delta should cool into the middle 70s overnight but those farther inland will cool off only into the lower 80s at night, the Weather Service said.

Most Foothills locations below 2,000 feet are expected to cool only to between 80 and 85 degrees again tonight. The heat index for today and Saturday will be near or above 105 degrees.

Meanwhile, the unusual and unrelenting heat wave that has gripped California for a week is driving yet another potential new record peak demand for power.

Energy demand is trending above forecast and is expected to beat Monday's record of 46,561 megawatts later today. Thursday's peak was just short of that at 46,465.

The California Independent System Operator is urging consumers to conserve power through Monday.