MEXICO CITY (AP) — Tropical Storm Julia formed Friday in the Caribbean Sea, triggering hurricane watches and warnings for Nicaragua and Colombian islands.

Julia had maximum sustained winds of 40 mph (65 kmh) late Friday afternoon and was moving west at 18 mph (30 kmh), according to the U.S. National Hurricane Center. The storm was about 450 miles (725 kilometers) east of Colombia’s Providencia Island.

Nicaragua issued a hurricane warning from Laguna de Perlas to Puerto Cabezas.

Julia is forecast to pass by Colombia’s San Andres and Providencia islands Saturday night on its way to landfall in Nicaragua early Sunday.

Colombian President Gustavo Petro said via Twitter that the government was preparing shelters on the islands. San Andres authorities announced a curfew for residents beginning at 6 a.m. Saturday to limit people in the streets.

Yolanda González, director of Colombia’s Hydrology, Meteorology and Environmental Studies Institute, said Julia could be a Category 1 hurricane when it passes the islands late Saturday.

A greater threat than Julia’s winds were rains of 5 to 10 inches (13 to 25 centimeters) — even 15 inches (38 centimeters) in isolated areas — that the storm was expected to dump across Central America.

“This rainfall may cause life-threatening flash floods and mudslides through this weekend,” the National Hurricane Center said.

Its remnants are forecast to sweep across Nicaragua, Honduras, El Salvador, Guatemala and southern Mexico, a region already saturated by weeks of heavy rains.