* WHAT. High temperatures in the 90s to 102 expected. Low temperatures in the mid 60s to lower 70s. * WHERE. San Diego County Mountains. * WHEN. From 10 AM this morning to 8 PM PDT Thursday. * IMPACTS. Hot temperatures may cause heat illnesses.

* WHAT. High temperatures for the inland valleys in the upper 90s to 106 expected. Low temperatures in the upper 60s to mid 70s for the far inland valleys near the foothills of the mountains. * WHERE. San Diego County Valleys. * WHEN. From 10 AM this morning to 8 PM PDT Thursday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events.

* WHAT. Dangerously hot conditions with temperatures from 108 to 115 expected. Low temperatures in the mid 70s to around 90 expected. * WHERE. Coachella Valley and San Diego County Deserts. * WHEN. From 10 AM this morning to 8 PM PDT Thursday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events.

Patchy dense fog with visibility of 1 nautical mile or less are expected tonight into Wednesday morning. Fog will lift and visibility will improve late Wednesday morning. Mariners should be prepared for sudden changes in visibility. Reduce speeds and be on the lookout for other vessels. Use radar or GPS navigation if available, and consider remaining in harbor if such equipment is unavailable.

* WHAT. High temperatures for the inland valleys in the upper 90s to 106 expected. Low temperatures in the upper 60s to mid 70s for the far inland valleys near the foothills of the mountains. * WHERE. San Diego County Valleys. * WHEN. Until 8 PM PDT Thursday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS. A few degrees of cooling are possible Thursday and Friday, but temperatures will remain well above average through the upcoming weekend.

* WHAT. High temperatures in the 90s to 102 expected. Low temperatures in the mid 60s to lower 70s. * WHERE. San Diego County Mountains. * WHEN. Until 8 PM PDT Thursday. * IMPACTS. Hot temperatures may cause heat illnesses. * ADDITIONAL DETAILS. A few degrees of cooling is possible Friday, but temperatures will remain well above average through the upcoming weekend.

* WHAT. Dangerously hot conditions with temperatures from 108 to 115 expected. Low temperatures in the mid 70s to around 90 expected. * WHERE. Coachella Valley and San Diego County Deserts. * WHEN. Until 8 PM PDT Thursday. * IMPACTS. Heat related illnesses increase significantly during extreme heat events. Warm overnight temperatures will lead to less relief from the heat, prolonging impacts. * ADDITIONAL DETAILS. Well above average temperatures will continue through the weekend.