Hurricane Lorenzo lost some force Sunday, weakening to a Category 4 storm after briefly escalating to Category 5 late Saturday.
The National Hurricane Center said the powerful storm is expected to pass over or near the Azores, the group of Portuguese islands about 900 miles west of Portugal on Tuesday.
"Steady weakening is expected over the next few days, but Lorenzo is still expected to be a potent hurricane in a couple of days," the center said.
The forecasters warned of heavy rains and life-threatening flash flooding on the islands.
"Lorenzo is expected to produce total rain accumulations of 3 to 6 inches over much of the western Azores and 1 to 2 inches over the central Azores on Tuesday and Wednesday. This rainfall could cause life-threatening flash flooding in the western Azores," the center said.
The NHC said Lorenzo has a wide wind field that could bring strong surf conditions to the beaches of the eastern United States and Canada, Western Europe and many Caribbean islands over the next few days.
Meanwhile, Tropical Storm Narda began pounding Mexico's Pacific Coast Sunday.
Narda was expected to dump up to 25 centimeters of rainfall along the Mexican coast from Oaxaca to Nayarit, including resort towns of Acapulco and Puerto Vallarta.