Jiachuan Yang.

Attribution of exposure temperature under heat waves.

Excessively hot or cold weather can contribute to higher rates of illness and death in cities, which house more than 80% of the U.S. population.

As climate change threatens more weather extremes, a new study looks at how daily commutes affect our exposure.

The research appears in the journal Science Advances.

Based on detailed models of weather and daily travel in 16 major U.S. cities, including Phoenix, the study found commuters faced temperatures averaging 3.4 degrees Fahrenheit hotter than expected for a given heatwave forecast.

One possible reason: working in areas more affected by urban heat island effects.

Co-author Chenghao Wang of Arizona State University worked on the research while earning his doctorate from the Department of Civil, Environmental and Sustainable Engineering. He said the study highlights the need to incorporate people's daily travels in assessing heat exposure.

"We cannot only consider the mean temperature across a city; we really need to think about how dynamic population can change the actual exposure," Wang said.

The authors say the findings could add detail to extreme weather warnings, which currently focus on broader areas and effects, and improve urban planning.