We describe Los Angeles County''s (LAC''s) usage of electronic emergency department (ED) and 911 emergency dispatch center (EDC) call data during heat waves for situational awareness. We assess the correlation between these indicators as well as with temperatures to conclude that total ED volume is not an adequate indicator for assessing the impact of heat on emergency service utilization. Heat-specific ED visits and EDC calls, however, provide more meaningful measures of heat-related illnesses in LAC.