More than 30 million people across a dozen states from California and Texas to Iowa are under a flood watch.
Flash flood watches are in effect from Phoenix, Arizona to Des Moines, Iowa, according to CBS News.
Flood watches cover a wide swath of the country, extending from the southwestern deserts through the Midwest, according to ABC News and CBS News.
More than 30 million people from Arizona to Iowa could be at risk for flash floods.
Maps show Hurricane Polo moving across Mexico's Baja California Sur toward the northeast at about 10 miles per hour, according to CBS News.
Hurricane Polo made its first landfall overnight along the Baja California Peninsula near Las Barrancas as a Category 2 hurricane, then downgraded to a Category 1 storm after moving across the peninsula and made a second landfall along the northwest coast of mainland Mexico, according to ABC News. It slammed the mainland as a Category 1 storm, arriving east of Guaymas with high winds and heavy rains, according to ABC News.
The storm's impact on the Mexican mainland included strong winds and heavy rainfall, with the core crossing the Gulf of California and moving toward Sonora, according to ABC News.
After making landfall in Baja California, Polo slammed the mainland of Mexico as a Category 1 storm, according to ABC News.
According to CBS News, the core of the storm will cross the Gulf of California and make a second landfall in Sonora, Mexico, and the storm is then expected to continue into the southwestern United States, nearing El Paso on Wednesday morning.
