Hurricane Maria hit Puerto Rico Wednesday morning and is expected to punish the U.S. territory with life-threatening winds for 12 to 24 hours, forecasters say.

Maria weakened slightly to a Category 4 hurricane overnight Wednesday before making landfall at Yabucoa, Puerto Rico, the U.S. National Hurricane Center said.

The hurricane was some 35 miles southeast of San Juan with maximum sustained winds of 155 miles per hour, the hurricane center said, and was moving northwest at 10 mph.

At one point, Maria had top sustained winds of 175 mph and was a Category 5 storm.

On the forecast track, Maria’s eye will “cross Puerto Rico today, and pass just north of the northeast coast of the Dominican Republic tonight and Thursday,” the center said.

Maria’s outer eyewall lashed the U.S. Virgin Island of St. Croix early Wednesday.

On Tuesday, the hurricane wreaked widespread devastation on Dominica, leaving the small Caribbean island virtually incommunicado.

As rains began to lash Puerto Rico Tuesday, Gov. Ricardo Rossello warned that Maria could hit “with a force and violence that we haven’t seen for several generations.”

“We’re going to lose a lot of infrastructure in Puerto Rico,” Rossello said, adding that a likely island wide power outage and communication blackout could last for days. “We’re going to have to rebuild.”

Authorities warned that people in wooden or flimsy homes should find safe shelter before the storm’s expected arrival Wednesday.

“You have to evacuate. Otherwise, you’re going to die,” said Hector Pesquera, the island’s public safety commissioner. “I don’t know how to make this any clearer.”

Gov. Ricardo Rossello said Puerto Rico had 500 shelters capable of taking in up to 133,000 people in a worst-case scenario. He said the Federal Emergency Management Agency (FEMA) was ready to bring drinking water and help restore power immediately after the storm.