Heavy rains, with the potential to cause flash flooding, are forecast by the US National Hurricane Center (NHC) for southern Texas and northeast Mexico as Potential Tropical Depression Four approaches land.
The disturbance is located about 200 miles (325 km) south-southeast of land.
On the forecast track, the disturbance is expected to reach the coast of northeastern Mexico late this afternoon and then move through the Rio Grande Valley tonight and Sunday.
A tropical storm warning is in effect for:
Coast of the Gulf of Mexico from Boca de Catan north to the mouth of the Rio Grande. Coast of Lower Texas from Port Mansfield south to mouth of Rio Grande.
The disturbance has maximum sustained winds near 35 mph (55 km/h).
The NHC said there is a chance the disturbance will strengthen slightly and become a tropical storm later today.
If that happens, the storm will be named Danielle.
