This is a scientific cliche describing a central fact of climate change. A warmer atmosphere can hold more water, about 4% more, which leads to more extreme weather. It's an idea that Kevin Trenbeth, who has published more than 400 scientific papers in climatology, has for a decade been translating into conversational English as "the wets get wetter and the dries get drier."
It's a well-understood phenomenon that this week in California took an interesting turn.
Here we have a surprisingly wet couple of days , in fairly heavy rains that hit the Bay on 6/24:
And here we have a huge drying out, as in a heat wave that looks likely to set all-time highs across the entire West, blankets the entire West just four days later:
The purple on the latest warnings map for some reason stands for red flag warnings.