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(CNN) Hurricane Fiona made landfall along the extreme southwestern coast of Puerto Rico, near Punta Tocon, at 3:20 p.m. ET Sunday with winds of 85 mph, according to the National Hurricane Center.
The hurricane is already causing catastrophic flooding as it moves just west of Puerto Rico and heads for the Dominican Republic, the center said in a 5 p.m. update.
The hurricane center is forecasting 12-18 inches of rainfall with a local maximum of 30 inches, particularly across eastern and southern Puerto Rico. Nearby in the norther and eastern parts of the Dominican Republic, 4-8 inches of rainfall is expected, with a local maximum of 12 inches possible along the northeast coast.
"These rains will produce life-threatening and catastrophic flash and urban flooding across Puerto Rico and the eastern Dominican Republic, along with mudslides and landslides in areas of higher terrain," the hurricane center said.
A flash flood emergency was issued for Sector San Felipe and Mosquito in Salinas County Sunday night as heavy rainfall pounded the region, where 10-15 inches of rain have already fallen, and another 2-4 inches are possible, according to the National Weather Service.
The heavy rainfall in Salinas County has already led to multiple swift water rescues, and the Weather Service is urging people to "move to higher ground now. Do not attempt to travel unless you are fleeing an area subject to flooding or under an evacuation order."
All of Puerto Rico lost power earlier Sunday, according to PowerOutage.us, as the Category 1 storm approached the islands.
Many rivers on the eastern side of the territory are in moderate to major flood stage. One river in the southeast has risen over 12 feet in less than seven hours and is now over 25 feet, breaking the previous record of 24.79 feet set in 2017 during Hurricane Maria.
Hurricane Fiona is the third of the 2022 Atlantic Hurricane Season and forecast to become a major hurricane -- a storm of Category 3 or higher -- in about 48 hours, east of the Bahamas.
Tropical storm conditions are expected to reach portions of the Dominican Republic within the next few hours and then in the Turks and Caicos Islands and portions of the southeastern Bahamas by early Tuesday.
The government of the Bahamas issued a tropical storm warning for the Turks and Caicos and for the Southeastern Bahamas, including the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana and the Ragged Islands.
The storm's impacts have already been felt: At least one death has been reported in Basse-Terre in the French territory of Guadeloupe, according to the vice president of the territory's environmental agency, who said the capital had been devastated by flooding.
Puerto Rico Gov. Pedro Pierluisi confirmed the territory-wide outage in a tweet, noting the entire electric system was out of service and officials have activated the proper protocols to work to restore power.
The Authority of Electric Energy and LUMA Energy, which operates Puerto Rico's power grid, continue to work on the islandwide power outage affecting nearly 1.5 million customers, according to Pierluisi.
The blackout -- which followed hours of progressively worsening power outages -- comes five years after Puerto Rico's power grid was devastated by Hurricane Maria in September 2017, leaving many residents without electricity for months.
But officials have stressed it won't be like last time: Not long before the lights went out, Abner Gomez, head of public safety and crisis management at LUMA Energy, said utility authorities plan to repair and restore electricity with the help of local government agencies. "This is not Maria, this hurricane will not be Maria," Gomez said.
President Joe Biden on Sunday morning approved an emergency declaration for Puerto Rico, freeing up federal resources, including the Federal Emergency Management Agency, for emergency response and disaster relief efforts.
There are more than 300 FEMA responders on the ground working "hand and glove" with the Commonwealth and their emergency management structure, Anne Bink, FEMA's Assistant Administrator for Response and Recovery, told CNN Sunday.
"Our heart goes out to the residents that are again going through another catastrophic event five years later," Bink said, noting Fiona has hit close to Hurricane Maria's five-year anniversary.
Bink said FEMA's response is dual focused, including emergency generation and power missions for critical facilities and ensuring command and control structure is in place for things like search and rescue, emergency power generations and long-term needs once the island moves into recovery.
Fiona's winds are expected to increase along the immediate coastline, while conditions are forecast to deteriorate throughout Sunday afternoon and evening, according to the National Weather Service's office in San Juan.
Already, authorities have responded to one landslide: Emergency officials responded Saturday evening to a landslide around 8 p.m. ET at an apartment complex in Guaynabo, according to fire and public safety officials. There were no initial reports of injuries.
Around 120 shelters with 25,000 cots have been opened for those in need, the governor said. Classes Monday have been canceled and government workers -- save emergency workers -- should stay home, too.
A hurricane warning -- indicating hurricane conditions are expected -- was issued for Puerto Rico, including the islands of Vieques and Culebra, and later expanded to include the eastern Dominican Republic from Cabo Caucedo to Cabo Frances Viejo. The Dominican Republic's northern coast, from Cabo Frances Viejo west to Puerto Plata, were under a hurricane watch Sunday morning, meaning hurricane conditions are possible in the next 48 hours.