TORONTO -- Airline officials will monitor Tropical Storm Isaac on Monday to determine whether it will be necessary to cancel more Toronto flights to Florida.

Flights out of Pearson International Airport to Florida were cancelled Sunday because of the storm, which is expected to strengthen into a Category 2 hurricane and hit the Gulf Coast somewhere between Florida and Louisiana by midweek -- on or near the seventh anniversary of Hurricane Katrina.

Scheduled Toronto flights to Miami were most affected Sunday, according to Scott Armstrong with the Greater Toronto Airport Authority.

But airlines were also cancelling flights to Tampa and Orlando as a precaution.

Armstrong urged travellers to go to torontopearson.com to check their flight status.

Travellers whose flights were cancelled will have to make new arrangements with their airline.

Tropical Storm Isaac lashed south Florida with winds and heavy rain on Sunday after battering the Caribbean, disrupting plans for the Republican National Convention in Tampa and threatening to interrupt about half of US offshore oil output.

A hurricane watch was extended westward to include New Orleans, which was devastated when Katrina struck the city on Aug. 29, 2005, killing more than 1,800 people and causing billions of dollars of damage to the Gulf Coast.

Isaac left six dead in Haiti and forced 14,000 to be evacuated from their homes.

In the Dominican Republic, officials say three people are missing, including the mayor of a town near Santo Domingo who was swept away as he tried to save another person from a flooded river. They reported 764 homes had been damaged and more than 9,600 people had to be evacuated from storm-struck areas.

Cuba was hit hard on Saturday with the storm forcing 1,000 people to be evacuated, according to Cuba TV.

A storm becomes a hurricane when sustained winds reach a minimum of 119 km/h.
-- With files from Reuters