Wildfires caused high levels of air pollution in San Francisco in November 2018. Climate change is making wildfires and heat waves more likely, and driving more days of unhealthy air in many U.S. cities.

Wildfires caused high levels of air pollution in San Francisco in November 2018. Climate change is making wildfires and heat waves more likely, and driving more days of unhealthy air in many U.S. cities.