(CNN) Even for a region accustomed to hurricanes, this storm has spawned a new level of fear.

Hurricane Matthew has already killed 15 people and threatens to flatten homes from Florida to the Carolinas.

"This is about as bad as it gets," National Hurricane Center Director Rick Knabb said.

So how bad is Matthew? Here's a look by the numbers:

145 mph: Expected strength upon landfall

By the time Matthew makes landfall in the US -- possibly early Friday on Florida's east coast -- it'll likely be a Category 4 hurricane, blasting 145-mph winds, forecasters said.

"This can be a devastating hurricane from both wind and water," Knabb said, "and that's why you have to take it seriously to stay alive."

2 million: Number of people urged to evacuate

The mandatory evacuations are the largest since Hurricane Sandy, which pummeled the US East Coast in 2012 and killed at least 147 people in North America.

About 1.5 million Floridians are in the evacuation zone. South Carolina has ordered hundreds of thousands to leave the coastal areas.

Even the 14,000 residents of the oldest city in the US -- St. Augustine, Florida -- have been told to evacuate.

15: Deaths caused by Matthew

Hurricane Matthew is the worst humanitarian disaster to strike Haiti since the 2010 earthquake, which killed more than 200,000 people, a United Nations representative in Haiti said.

Matthew killed at least 10 people in Haiti, where tens of thousands still live in makeshift homes after the earthquake.

Adding to the humanitarian crisis: National Route 2, which connects Port-au-Prince with Haiti's devastated southern peninsula, broke apart when a bridge collapsed -- severely hampering relief efforts.

Matthew killed another four people in the Dominican Republic as well as a teenage boy in St. Vincent and the Grenadines.

1,500: Flights canceled

As of Wednesday morning, about 1,500 flights have been canceled as Matthew approaches the southeastern US. That number could rise as the hurricane starts thrashing the coast.