Increasingly extreme heat is contributing to more deaths in California. Why getting data is so slow

July’s record-breaking heat is suspected to have contributed to dozens of deaths across California, and likely far more , but it could be months before we know the heat’s true death toll.

The background

July was California’s hottest month in at least 175 years , a sign of how the pollution spewed by human society is rapidly changing our climate and making heat waves more dangerous.

Why it matters

Public health experts say long lags in data on how increasingly extreme heat waves affect health and mortality can hurt timely and effective prevention efforts.

Why it takes so long

It can take months to assess all the factors that may have contributed to a person’s death before authorities can determine the likely cause in a coroner’s report. Public health departments can also conduct “excess mortality” analyses, which compare the number of total deaths that occurred during a period of extreme heat with the number of deaths that occur under normal conditions.

When will we have the numbers?

The L.A. County Medical Examiner’s Office said it expects to have heat-related death data by October. It can take six to 18 months for the California Department of Public Health to compile data for heat-related deaths statewide.

The most recent data

The state’s last “excess mortality” report was published nearly a year after a record long and hot September heat wave in 2022. In it, they determined at least 395 additional deaths occurred as a result of that heat wave. Research from UCLA has found that between 2009 and 2018, there are on average 1,177 additional emergency room visits on days that are 90 degrees or hotter.

What’s next

UCLA is expected to publish an update on its heat-related emergency room visit data later this year. The state is working to launch a centralized data system that tracks real-time heat related emergencies.