* WHAT. Dangerously hot conditions with temperatures up to 99 possible. * WHERE. Eastern San Fernando Valley, Interstate 5 Corridor, Santa Barbara County Interior Mountains, Santa Clarita Valley, Santa Lucia Mountains, Santa Ynez Mountains Eastern Range, Santa Ynez Mountains Western Range, Western San Fernando Valley, and Western San Gabriel Mountains and Highway 14 Corridor. * WHEN. From Saturday morning through Monday evening. * IMPACTS. There is a high risk for dangerous heat illness for anyone, especially for the very young, the very old, those without air conditioning, and those active outdoors.

* WHAT. Dangerously hot conditions with high temperatures of 98 to 108 degrees expected. Highest temperatures will be in the valleys, lower foothills and Santa Monica Mountains. Overnight lows will be in the 60s and 70s, except lower 80s in some foothill locations. * WHERE. Most mountains and valley areas. * WHEN. From 10 AM Saturday to 8 PM PDT Monday. * IMPACTS. There is a high risk for dangerous heat illness for anyone, especially for the very young, the very old, those without air conditioning, and those active outdoors. * ADDITIONAL DETAILS. It will be very dangerous to perform strenuous activities during the late morning through early evening hours over the weekend. Use extreme caution when hiking or biking, even in the popular Santa Monica Mountains, as some of the hottest conditions will be in that location. Heat Advisories may be needed for interior portions of the coastal plain, including Downtown Los Angeles.