* WHAT...For the Dense Fog Advisory, visibility one quarter mile or less in dense fog. For the Extreme Heat Warning, Dangerously hot conditions with temperatures up to 90 at the coast and 105 in the valleys. * WHERE...Malibu Coast and Ventura County Beaches. * WHEN...For the Dense Fog Advisory, until 10 AM PDT this morning. For the Extreme Heat Warning, from 10 AM this morning to 8 PM PDT Thursday. * IMPACTS...Heat related illnesses increase significantly during extreme heat events. Low visibility could make driving conditions hazardous. * ADDITIONAL DETAILS...Very hot temperatures are likely to continue into the second week of October, possibly requiring an extension of this product.