A record-breaking heat wave sweeping across the U.S. and Europe is being driven by fossil fuel pollution and made more dangerous by nighttime temperatures that offer little relief.

Andrew Freedman reports for CNN.

“Every heatwave that is occurring today is hotter than it would have been without human-induced climate change.”

— Fredi Otto, climate scientist and lead of the World Weather Attribution project

Why this matters:

Heat waves are no longer isolated or predictable — they’re intensifying, spreading, and striking earlier in the season, catching people and infrastructure unprepared. As global temperatures rise, these events are becoming more humid and longer-lasting, which increases their threat to human health. Hotter nights deny the body time to recover, particularly for the elderly, infants, and those with chronic conditions. Urban areas bear the brunt due to heat-trapping buildings and pavement.

The implications stretch beyond health: Heat stresses power grids, warps roads and railways, and damages crops, threatening food security. While storms and floods draw dramatic headlines, heat quietly kills more Americans each year than any other weather hazard. And climate models may be underplaying what’s still to come.

Related: How youth can battle extreme heat in their communities