Over recent years, summers have seemingly seeped into ever-lengthening seasons of climate disruption. Wildfires blaze through vast swaths of forest in the American West and across Canada, releasing smoke that drifts thousands of miles and casts an eerie orange glow over East Coast cities.

The same stubborn atmospheric patterns that feed these infernos also blanket urban centers like Philadelphia in relentless, punishing heat. Heat domes settle over concrete corridors—especially in low-income neighborhoods with limited green space—turning row homes, buses, and sidewalks into sweltering hazards.

Presidential Distinguished Professor in Penn’s Department of Earth and Environmental Science Michael E. Mann, postdoctoral researcher Xueke Li, and other researchers offer fresh insight into the atmospheric mechanics behind these extremes—and troubling evidence that they’re becoming more common. Read more about their findings at Penn Today.