The National Weather Service in Brownsville has expanded the Flash Flood Watch to include a portion of Deep South Texas, including the following areas, Coastal Cameron, Coastal Willacy, Inland Cameron, Inland Willacy, Northern Hidalgo, and Southern Hidalgo through Wednesday evening.
Forecasters say widespread and slow moving rain caused by deep tropical moisture over the area and a low pressure system is to blame for the storms in the Valley.
An additional three to five inches could hit the area through Wednesday night, with some areas getting four to six inches or more.
The NWS warns the heavy rains could cause small streams to flood and any low-lying areas could see upwards of a foot of water.
The National Weather Service in Brownsville has issued a small stream flood advisory for Cameron and Willacy counties until 4:15 p.m.
Forecasters say Doppler radar the heavy rain is due to a number of thunderstorms throughout the region.
Heavy rain is expected in Los Fresnos, South Padre Island, Rancho Viejo, Rio Hondo, Arroyo City, Southmost, Olmito, La Paloma, Cameron Park and Laureles.
Another two inches of rain is possible in these communities. On Monday many areas of Harlingen reported up to five inches of rain, with widespread street flooding.