Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.

* WHAT...Dangerously hot conditions with daytime temperatures up to 104 degrees expected and overnight low temperatures offering little reprieve from the heat. * WHERE...Interstate 5 Corridor and Western San Gabriel Mountains and Highway 14 Corridor. * WHEN...Until 8 PM PDT Thursday. * 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.