Numerous flights from Toronto’s Pearson airport have been cancelled due to tropical storm Isaac, which is due to make landfall in the Florida Keys on Sunday.

Flights to Miami and Fort Lauderdale were cancelled and several others were delayed.

Click here for the full list of departures.

New Orleans was the latest major United States city to be added to the National Hurricane Center watch area. The area now includes the coast from east of Morgan City, Louisiana to the Florida Panhandle.

The Republican National Convention has canceled the program’s first day due to the storm, and the band Lynard Skynard also cancelled a Florida concert.

“Some of the delegates have never been around a hurricane,” Florida governor Rick Scott said. He urged those coming for the convention to be cautious and promised to help other affected areas.

“We’re worried about what’s going to happen to Florida and we’re going to need to help other states…If it ends up going further west, Florida is ready to be helpful.”

Tropical storm Isaac has killed at least four people in Haiti and blasted Cuba with winds and rain on Sunday as it swept toward Florida, where it is expected to strike as a minor hurricane.

The storm also damaged a massive tent city in Port-au-Prince, where more than 350,000 people are still living following Haiti’s devastating 2010 earthquake.

Isaac’s winds have been clocked up to 100 kilometres an hour, and forecasters say they could reach official hurricane strength of 120 kilometres by the time the storm’s eye reaches the Keys Sunday night.

Areas around the Florida Keys are also expected to be drenched by 150-millimetres of rain, which, along with the storm surge, has some worried about flooding.

Officials in Florida have warned that if the peak storm surge comes at high tide some low-lying areas could be swamped with flooding up to 2-metres deep.

With files from 680News and CNN