* WHAT. Dangerously hot conditions with daytime temperatures up to 109 degrees expected. Overnight low temperatures will offer little reprieve from the heat. * WHERE. Eastern San Fernando Valley, Santa Clarita Valley, and Western San Fernando Valley. * 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.

* WHAT. Dangerously hot conditions with daytime temperatures up to 109 degrees expected. Overnight low temperatures will offer little reprieve from the heat. * WHERE. Eastern San Fernando Valley, Santa Clarita Valley, and Western San Fernando Valley. * 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.

* WHAT. Dangerously hot conditions with daytime temperatures up to 109 degrees expected. Overnight low temperatures will offer little reprieve from the heat. * WHERE. Eastern San Fernando Valley, Santa Clarita Valley, and Western San Fernando Valley. * 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.

A shallow marine inversion will continue to bring dense fog to most of the coastal waters through at least tomorrow morning, and will be most widespread in the overnight thru morning hours. Mariners should be prepared for abrupt visibility changes down to one nautical mile or less. Reduce speeds and be on the lookout for exposed rocks and other vessels, including large ships in the shipping lanes. Use radar or GPS navigation if available, and consider remaining in harbor if such equipment is unavailable.

* WHAT. Dangerously hot conditions with daytime temperatures up to 109 degrees expected. Overnight low temperatures will offer little reprieve from the heat. * WHERE. Eastern San Fernando Valley, Santa Clarita Valley, and Western San Fernando Valley. * 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.