STORY: The entire island of Puerto Rico was without power on Sunday as Hurricane Fiona made landfall and threatened to cause "catastrophic flooding" and landslides.

Puerto Rico's governor Pedro Pierluisi:

"Because of the storm's size, this storm will impact all of Puerto Rico. The flood warning for all of Puerto Rico is extended until Monday.”

The storm knocked out the territory's power grid -- which remains fragile after Hurricane Maria caused the largest blackout in U.S. history in 2017.

(Estefani Lee, Resident of Ponce)

“I think we have learned a lot from the last time, we didn’t prepare because we thought nothing bad would happen, and look what happened. So this is why we really prepared this time and bought a power generator."

The storm made landfall with maximum sustained winds of over 85 miles per hour -- according to the National Hurricane Centre.

U.S. President Joe Biden declared a state of emergency Sunday.

The move authorizes the Federal Emergency Management Agency to coordinate disaster relief.

Authorities have opened up more than 100 shelters and are urging people to take cover.

The storm is already being blamed for at least one death.

Puerto Rico's ports have been closed and flights out of the main airport canceled.

Torrential rains and mudslides were also forecast for the Dominican Republic as the storm progresses northwest, with the Turks and Caicos Islands likely facing tropical storm conditions on Tuesday.