Tropical Storm Eta has hit Florida, flooding roads and knocking out power in some areas with heavy rain and strong winds.
Eta made landfall late on Sunday in the Florida Keys and forecasters fear it could still cause flash-flooding in the southern US state.
The storm is now moving south-west and is expected to slow and strengthen over the Gulf of Mexico.
About 200 people are dead or missing after Eta hit Central America.
Earlier classified as a hurricane before losing strength, Eta wreaked devastation in Panama, Honduras and Guatemala. It also passed through Cuba before making landfall in Florida.
Pictures posted on social media from the region showed houses with water up to their roofs and flooded fields. In Florida residents posted video of howling wind and driving rain.
A relief operation is underway in Honduras after two major rivers overflowed, trapping tens of thousands of people on the roofs of their homes.
In a statement, Queen Elizabeth II said: "Prince Philip and I were deeply saddened by the tragic loss of life and destruction caused by Hurricane Eta.
"Our thoughts and prayers are with those who have been injured or lost their lives, and all those whose homes and livelihoods have been affected."
What's the latest on Eta?
After warning earlier that parts of Florida could see "life-threatening flooding", the National Hurricane Centre (NHC) advised on Monday afternoon that the storm is moving south-west towards the Gulf of Mexico.
The storm is expected to slow down and strengthen on Monday night into Tuesday, it said.
"Eta could approach the Florida Gulf Coast later this week as a tropical storm, and possibly bring impacts from rain, wind, and storm surge," the advisory said.
Additional flash flooding in inundated urban parts of south-east Florida remains possible, it cautioned.
It said "flash and urban flooding will also be possible for Jamaica, the Bahamas, and the remainder of southern and eastern Florida over the next several days".
On Sunday, in preparation for Eta, officials in Miami-Dade and Broward counties, and in the Keys, ordered the closure of all schools, beaches and public transport. Mobile home parks and campgrounds in low-lying areas were also evacuated and shelters open.
"Please take this storm seriously," Palm Beach County Emergency Management Director Bill Johnson urged residents, adding: "Please don't drive through flooded roadways."
Tens of thousands of people were evacuated in Cuba ahead of the arrival of Eta amid warnings of "significant, life-threatening flash and river flooding". However, state media reported that there had been "no loss of life or significant damage to homes".
Other parts of the region have not been so lucky.
Some 150 people are dead or missing in Guatemala after dozens of homes were buried by mudslides in the central region of Alta Verapaz. Large parts of neighbouring Honduras are under water and the number of deaths doubled on Monday to reach at least 57 while eight people were reported missing.
Panama has reported 17 deaths and 68 people are missing, Security Minister Juan Pino said. In Mexico, officials in the southern state of Chiapas said the storm had claimed at least 20 lives.