GULF COAST — The National Weather Service issued warnings for ongoing and potential flash flooding, severe weather, and extreme heat across multiple regions of the U.S. Heat alerts are in effect for parts of the West.

Flooding has occurred across the southern region. At least 16 million people are under flood watches from southern Texas through central Mississippi along the Gulf Coast. These flood watches are expected to expand to include Alabama on Tuesday, and a moderate flood risk warning is in effect for parts of Texas, Louisiana, Mississippi, and Alabama for three days.

Video footage from Texas and the Gulf Coast shows roads covered and vehicles submerged by floodwaters. One video shows a person jumping from a tree to reach first responders while trapped in floodwaters. Officials in the Texas Hill Country are searching for a vehicle and driver swept away on Monday morning. Recovered vehicle parts indicated the driver and vehicle may be located further downstream, according to Bandera County Sheriff Joshua Teitge.

The FIFA Fan Fest in Houston was canceled due to heavy rain. Cities at risk include Corpus Christi, Houston, Galveston, and Beaumont in Texas; Lafayette, Alexandria, and Baton Rouge in Louisiana; Montgomery and Birmingham in Alabama; and Jackson, Mississippi. New Orleans has the highest flood risk in the region.

Rainfall rates of 2 to 5 inches per hour are forecast, with totals through Friday expected to reach 8 to 10 inches and up to 12 inches locally. Tropical moisture is contributing to the increased rainfall and flood risk. This moisture originates from a weather disturbance near the Mexico and Texas border, which meteorologists assigned a 60 percent chance of development within two to seven days as of Tuesday morning. The disturbance could develop into a short-lived tropical storm on Tuesday or Wednesday if it moves over the Gulf of Mexico. Flash flooding, gusty winds, rip currents, and waterspouts are possible along the Gulf Coast in the coming days.

Separately, severe weather and possible tornado activity could affect 38 million people from Kansas to Ohio in the Midwest and Ohio Valley on Wednesday. Wind gusts exceeding 75 mph are forecast in this affected region. This severe weather risk is expected to extend from Kentucky and Tennessee to Long Island on Thursday.

Heat alerts are in effect for 13 million people across the Pacific Northwest, California, and the southern Rockies. Temperatures are forecast to be 5 to 20 degrees above average in these areas, increasing fire danger in the western regions.