Increased temperatures and heatwaves are already serious public health problems in the United States and will worsen as climate change increases their frequency and intensity. Heat’s direct public health impacts include heat stress and stroke, death, and worsening of cardiovascular and respiratory diseases. Heat also degrades air and water quality, causing secondary impacts as well. Heat does not affect everyone equally – some populations are physically more susceptible to its effects, and others can be more vulnerable due to their environments. Governments owe particular legal duties to some of these populations under federal and state law.

Interventions to reduce the negative health effects of heatwaves and higher temperatures fall into two categories: emergency response strategies that include mostly traditional local public health functions, and built environment strategies that use a wider array of government powers, such as changes to zoning and building codes.