Hurricane Fiona is forecast to become the season's first major hurricane in the Atlantic, as it continues to unleash heavy rains on Puerto Rico and the Dominican Republic.

The latest: Fiona, which strengthened into a Category 2 storm Monday, has killed at least two people — one in Puerto Rico and another in the Dominican Republic, while at least one death has been linked to the widespread power outages Fiona caused in Puerto Rico, AP reports. The 70-year-old man died trying to refill his generator, officials said.

12:15 AM AST Sep 20: Line of showers and thunderstorms mostly affecting southwestern Puerto Rico
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Líneas de aguaceros y tronadas afectando mayormente al suroeste de Puerto Rico. #PRwx #USVIwx pic.twitter.com/Q5e6Epvtdm

— NWS San Juan (@NWSSanJuan) September 20, 2022

Threat level: Fiona was packing maximum sustained winds of 110 mph some 80 miles southeast of Grand Turk Island late Monday, as it dumped heavy rains across Puerto Rico and parts of the Dominican Republic — where "life-threatening" flash flooding was likely, per the National Hurricane Center.

• Mudslides and landslides were still a risk for Puerto Rico, the NHC said in an 11pm ET forecast update.

What we're watching: Though Puerto Rico and the Dominican Republic have taken the worst hits so far, Fiona was expected to also pose a threat to the Turks and Caicos Islands as well as Bermuda.

• The hurricane was expected to develop into a Category 3 storm near the Turks and Caicos by Tuesday morning.

What they're saying: The White House said Monday the federal government has deployed 300 personnel to Puerto Rico to assist with response and recovery.

• President Biden spoke with Puerto Rico Gov. Pedro Pierluisi about the federal government's support and the "number of support personnel will increase substantially" in the coming days once damage assessments have been conducted, according to a White House statement.

The big picture: Fiona left over 1.4 million people in Puerto Rico without power on Sunday as it caused an island-wide outage five years after Hurricane Maria struck. Pierluisi said Monday it may be days before power's restored.

• Rapidly rising waterways have led rivers to crest at record heights.
• After pummeling Puerto Rico, the hurricane slammed into the Dominican Republic on Monday, triggering mudslides that damaged highways and forced resorts to close.

Go deeper: Three massive storms slam U.S. and Japan, each with climate change ties

Editor's note: This is a breaking news story. Please check back for updates.