PARIS • Meteorologists attribute the recent deluge to a dip in the jet stream that has trapped low-pressure air over much of France and Germany, where the air is then warmed by the sun. This occurrence often leads to heatwaves, and to thunderstorms as the hot air rises. The recent thunderstorms have been more intense than usual because the hot air rises to encounter colder air in the upper atmosphere. The greater the difference between the rising hot air and the colder high air, the bigger the storms. Forecasters say there could be a few more days of rain before the low-pressure air finally moves on.
NEW YORK TIMES