Moisture from the Gulf of Mexico began to unleash heavy rain across the southern United States on Monday, threatening the region with flash floods and rising waterways, as torrential rain fell over parts of northern California.

On Sunday, downpours were reported in southern and central Texas, where flood warnings were issued by the National Weather Service ahead of additional storms. Parts of Houston had collected up to 4 inches of rain early Monday. Sections of major highways in San Antonio were shut down because of flooding.

More than 11,000 utility customers in Texas were without power Monday morning, according to a database maintained by USA TODAY.

Throughout the week, the swath of moisture will bring between 2 to 4 inches of rain from Texas to northern Georgia, western North Carolina and West Virginia, according to AccuWeather. The week's heaviest rainfall is forecast to hit parts of Louisiana, Mississippi, Alabama and Tennessee.

Thunderstorms expected to break out in states along the Gulf Coast on Tuesday and Wednesday could have damaging storms winds with gusts as high as 70 mph, AccuWeather said.

'Weather whiplash:'Out of the freezer and into the warmth with rain, flooding this week

Storms in northern California; freezing rain to lash Midwest

In northern California, heavy rain is expected throughout the week. Coastal and flash flood warnings were active in northern California and southern Oregon on Monday, according to the weather service.

Residents in some parts of Sonoma County in northern California, which encompasses Santa Rosa, were told to prepare for evacuations amid local flooding and downpours. Downed trees closed major roads and caused damage throughout the Bay Area overnight and early Monday morning. Over 6,800 households were without power, according to a USA TODAY database.

A lull in the wet weather will follow on Tuesday before more downpours are forecast for northern California.

As the artic air that plunged temperatures in the Plains, Midwest and Northeast into single digits over the weekend moves east, the channel of moisture will quickly follow in its path, the weather service said. Over the week, parts of the Midwest will receive periods of freezing rain and sleet as temperatures rise. The first rain is expected in the lower Great Lakes by Monday night.