Several countries in Europe have issued heat alerts as extreme temperatures soar across the continent. The blistering temperatures were caused by a “heat dome,” a high-pressure system that traps hot air moving from northern Africa that can drive up heat and humidity.

Temperatures climbed above 100 degrees Fahrenheit across parts of Europe, creating health concerns and causing landmarks to close.

A punishing heat wave broke records in southern Europe and hasn’t peaked yet in some places, prompting warnings to residents, employers and tourists to alter their habits.