Tropical Storm Isaias formed early Wednesday in the warm waters off eastern Mexico, and forecasters said it was expected to strengthen into the first hurricane of the Atlantic season before hitting the US Gulf Coast later in the week.

Isaias was located about 285 miles (460 kilometers) west of Progreso, Mexico, and about 580 miles (935 kilometers) southwest of the Mississippi River's mouth, according to the Miami-based National Hurricane Centre. It had maximum sustained winds of 40 mph (65 kph) and was moving east-northeast at 8 mph (13 kph).