A 58-year-old woman suffered cardiac arrest in her home in central Florida's St Lucie County overnight, but high winds from Matthew - then a major Category Three storm on a scale of one to five - prevented fire officials from reaching her, a fire spokeswoman told AFP on Friday.
"We were unable to respond safely, and unfortunately she died," said St Lucie County Fire District spokeswoman Catherine Chaney.
In the early morning hours, rescuers also received a call about an 82-year-old man who was experiencing stroke-like symptoms and was having difficulty breathing. "Again, we could not go because that's when the winds were high," Chaney said.
The man was taken in a personal vehicle to a nearby hospital, and fire officials learned later that he died, she said. At midday on Friday, a woman in Volusia County ventured outside to feed some animals during a lull in the storm and was killed by a falling tree, said county manager Jim Dinneen.
The powerful storm surged through the Caribbean earlier this week, at times as a powerful Category 5 hurricane, killing more than 400 people in Haiti and four in the Dominican Republic. Matthew was downgraded to Category 2 storm on Friday as it pummelled the northeastern Florida coast with winds of 175 kilometers per hour.