MEXICO CITY >> Tropical Storm Boris formed off Mexico’s Pacific coast on Tuesday, forcing evacuations in seaside and mountain communities vulnerable to flooding and mudslides.

Boris was forecast to bring torrential rains to coastal states such as Chiapas and Oaxaca.

The Chiapas state civil defense office said it had already evacuated about 300 people from around the coastal community of Arriaga, and that further evacuations were planned.

The state cancelled classes in many areas, and mud and rockslides have already occurred on some state roads.

The U.S. National Hurricane Center in Miami said Boris was centered about 125 miles southeast of Salina Cruz on Tuesday. It was moving north at about 5 mph and had maximum sustained winds of about 40 mph.

Its current track would take it almost directly across the narrow waist of Mexico that separates the Gulf of Mexico from the Pacific.

A tropical storm warning was in effect in southern Mexico from Salina Cruz to Mexico’s border with Guatemala.

Forecasters said tropical storm conditions were already reaching the coast, with nearly 4 inches  of rain reported in Puerto Chiapas.

Boris could produce as much as 10 to 20 inches of rain over southern Mexico in the coming days, creating the risk of deadly floods and mudslides.