Tropical Storm Boris formed off Mexico’s Pacific coast, threatening the southern part of the country with heavy rain and “life-threatening” floods through the weekend.

The system was 125 miles (200 kilometers) southeast of Salina Cruz, Mexico, as of 2 p.m. New York time, moving north at 5 mph with maximum sustained winds of 40 mph, the U.S. National Hurricane Center said in an advisory. Boris is expected to drop 10 to 20 inches (25 to 50 centimeters) of rain in the region, with some mountain areas getting as much as 30 inches.

“These rains are likely to result in life-threatening flash floods and mudslides,” the center said.

At least five people were killed as heavy rain fell in neighboring Guatemala, triggering a landslide, the Associated Press said, citing Alejandro Maldonado of the National Office for Disaster Reduction. The storm is expected to move slowly inland this week, so rain may soak the area for days.

Puerto Chiapas, Mexico, had received 3.8 inches of rain by midday, the hurricane center said.

“They are going to get hammered with quite a bit of rain,” said Brian Wimer, an expert senior meteorologist at AccuWeather Inc. in State College, Pennsylvania. “This is a classic setup with rain coming in, and once you get away from the coast there are some pretty high mountains, and that helps enhance the rainfall.”

Moving North

Wimer said there’s a slight chance the remnants of the storm will enter the Bay of Campeche in the Gulf of Mexico late this week. He doesn’t think it will re-form into a storm there.

“It doesn’t look like a great setup but it is something to keep an eye on,” Wimer said.

A tropical storm warning is in place from Salina Cruz, Mexico, to the border with Guatemala.

Boris is the second tropical storm of the Eastern Pacific hurricane season, which began May 15. Storm Amanda grew into a Category 4 major hurricane without directly threatening land.

The hurricane center is also tracking a disturbance in the Bay of Campeche, in the southern Gulf on Mexico. It has a 20 percent chance of growing into a tropical system in the next five days.