Guam residents rushed to prepare for what is expected to be a life threatening typhoon, a storm potentially so severe that President Joe Biden signed an emergency declaration Tuesday to mobilize resources.

Super Typhoon Mawar is expected to be a “triple threat” of torrential rains, life-threatening storm surge and Category 4 hurricane-force winds, according to Guam’s Homeland Security Department.

“This is a very serious situation with steadily deteriorating conditions,” the department said.

The National Weather Service said the storm could hit southern Guam around midday Wednesday, which is Tuesday evening in the continental United States. Guam lies to the west of the International Date Line and is nearly a day ahead of the U.S. mainland.