Just in time for the Fourth of July, the first major heat wave of the summer continues in the Southland today, with forecasters warning of  “dangerously hot” conditions in some areas.

An excessive heat warning will be in effect from 10 a.m. Saturday through 8 p.m. Sunday in the Santa Clarita Valley, the Antelope Valley and the foothills. Those areas could see temperatures of 100 to 112 degrees, according to the National Weather Service, which warned of the potential for heat-related illnesses.

A less-severe heat advisory will be in effect during the same hours in the western San Gabriel Valleys and the 5 and 14 freeway corridors. Temperatures in those areas are expected to range from the mid-90s to 105 degrees.

Long Beach and other coastal areas will be much cooler, with temperatures in the mid-70s for much of the weekend and early next week. The hottest day in Long Beach will be 78 degrees on Monday, the NWS predicts.

The heat is the result of a building high-pressure system, which will bake inland areas.

Beaches are expected to be popular destinations for the weekend, with forecasters noting that “a persistent marine layer and onshore flow” will keep temperatures down in coastal areas.