* WHAT...High temperatures of 92 to 105 expected, with most areas seeing peak heat on Wednesday and Thursday. Low temperatures are expected to range from the upper 60s to lower 70s at lower elevations to the mid 70s to lower 80s in the foothills and mountains. * WHERE...A portion of southwest California. * WHEN...From 10 AM Tuesday to 8 PM PDT Thursday. * IMPACTS...Hot temperatures may cause heat illnesses. Warmer than normal low temperatures will add to the heat discomfort. * ADDITIONAL DETAILS...The heat advisory may need to be extended into Friday for portions of the forecast area, but there remains considerable uncertainty at this time.