U.S. — As Irma makes its way towards the eastern U.S., it has now been upgraded from a tropical storm to a Category 5 hurricane.

Hurricanes are classified into five categories using the Saffir-Simpson scale, with the highest number representing the most powerful storm.

Hurricanes are categorized based on wind speed. The wind speed is measured from an unobstructed area at a point 33 feet (10 meters) above the ground for one minute, according to the National Hurricane Center.

The higher the category, the stronger the winds, and the more damage to be expected.

Storms moving less than 38 mph are classified as a tropical depression, while those moving between 39 to 73 mph are considered tropical storms.

In a Category 1 hurricane, wind speeds blow between 74 to 95 mph. Downed power lines, broken tree limbs, and minor home damage can be expected.

With a Category 2 hurricane, wind speeds are between 96 to 110 mph. There can be "extensive damage" to houses and trees, while power outages can last for days or weeks.

A Category 3 has wind speeds from 111 to 129 mph and the potential to cause "devastating damage" to roof decking and gable ends.

In a Category 4 hurricane, wind speeds range from 130 to 156 mph and have the ability to cause "catastrophic damage," with the possibility of leaving areas uninhabitable for weeks to months.

The last is a Category 5, which has wind speeds of 157 mph and over. During a Category 5, there's a "high percentage" that a home can be totally destroyed.