Tropical storm watches and warnings have been extended westward along Mexico's coast as tropical storm Frank churns slowly in the Pacific.

Meanwhile, tropical storm Danielle is getting stronger far out over the Atlantic.

On Monday, Mexico discontinued a tropical storm warning east of Puerto Escondido but extended it from west of Tecpan de Galeana to Zihuatanejo. A tropical storm watch has been extended westward to Punta San Telmo.

Frank has maximum sustained winds near 95 kilometres per hour and it's possible it could become a hurricane by late Monday night.

The storm is located about 170 kilometres south-southwest of Puerto Escondido, Mexico, and is expected to move parallel along the southern coast through Tuesday.