Strong to severe thunderstorms will be possible Tuesday for millions of people who live in the Northeast.
Large hail, damaging winds, and isolated tornadoes will be possible along with heavy rain, which could lead to flash flooding.
Parts of the Southwest could see some heavy rain as well on Tuesday and Wednesday.
Flood advisories are in effect from Nevada through Arizona and Utah and New Mexico.
As temperatures come down in the West, the heat will build over the Plains and Mississippi Valley.