The New York Times writes today about the challenges of collecting data on heat deaths ("Heat Kills, but It's Hard to Say How Many"). Accurate data is important for targeting preventive measures, but reliable data is not easily obtained. Essentially, the problem is that heat can exacerbate other conditions. For example, a person may have a preexisting heart condition. If that person dies during an exteme heat event, should the death be attributed to the heat or to the heart condition? The Times reports that the criteria for making such judgements are not always clear and or consistently applied, and medical examiners often do not have the resources to fully investigate the causes of each death. Moving to less ad hoc data collection systems can be costly for local governments.
The Centers for Disease Control and Prevention (CDC) introduced a form in 2017 to help investigators ascertain heat-related deaths, although the article notes that the CDC is not currently tracking the use of these forms. The article also reports that the CDC is currently developing a framework for determining "excess deaths" from heat-related causes based on historical data.