LOS ANGELES - As the Eastern Seaboard battens down for a post- earthquake hurricane, Southern Californians are being warned about "dangerous" heat, possible gullywashers in the mountains and deserts, and a monstrous shark cruising off one popular beach.

An excessive heat warning was issued for Southland mountains and valleys today, with highs up to 112 possible in the warmest reaches of the Antelope Valley and Inland Empire. Inland Orange County, as well as the Santa Clarita, San Fernando and San Gabriel valleys, may see readings nudging 107.

A series of thunderstorms hit the Lake Havasu area overnight, and that pulse of monsoon moisture may move into the mountains and deserts of Riverside, San Bernardino, Los Angeles and Ventura counties. That raises the possibility of severe, localized thunderstorms in the mountains and deserts of Los Angeles County later today, the National Weather Service predicted.

To complete the tableau, a 14-foot shark's fin has been spotted twice, cruising the waters off Mission Beach in San Diego, a favorite spot for Angelenos and Inland Empire residents to travel to. Lifeguards have twice closed the waters off Belmont Park, but reopened them.