As of this writing, Hurricane Florence is making its way to the east coast of the United States, and it is expected to do extreme damage to several states along the coast. Virginia, North Carolina and South Carolina have already declared a state of emergency. Mandatory evacuations have been issued to millions of people.

How much damage Florence will do depends on a few things. If it slows down by the coast as some expect it to, the massive flooding that is anticipated could become much worse.

What will also play an important role is the category of hurricane it is when the effects reach land. Residents of states in a state of emergency or living near the shore on the east coast will need to be prepared, stock up on supplies and, if need be, evacuate as soon as possible.

If you're wondering how hurricane categories are determined, it is based on the Saffir-Simpson scale.

Saffir-Simpson Scale

Categories of hurricanes determine more than the damage potential for a storm, they may also trigger the deductible in a person's hurricane insurance.

The Saffir-Simpson scale was first introduced in 1973, and was named after its developers: Herbert Saffir, an engineer, and Robert Simpson, at the time the director of the National Hurricane Center.

Over the ensuing decades, the scale would go through changes. Today, it uses Categories 1-5 to measure the wind scale of the hurricane, and the damage it can do as a result of the wind.

Don't be fooled by the degrees between Category 1 and Category 5. Category 1 may be the least dangerous hurricane on the Saffir-Simpson Scale, but it's still a hurricane, and the U.S. has seen Category 1 hurricanes leave states in bad shape for weeks, and even years.

Category 1 Hurricane

What makes it a Category 1 hurricane instead of a tropical storm? According to the Saffir-Simpson scale, gusting winds from 74-95 miles per hour, capable of damage to power lines and causing outages. As large tree branches could snap as a result of these gusts, it's possible for some surface-level damage to be done to a house, but it's unlikely that structural damage could occur to a home with a sound structure.

An example of a Category 1 hurricane would be Hurricane Isaac in 2012, which peaked at Category 1 but lessened to a tropical storm as it reached further inland.

Category 2 Hurricane

Category 2 hurricanes have much more dangerous winds that often break past 100 mph, generally in a 96-110 mph range. Power outages are far more likely and longer-lasting than with a Category 1, and trees with shallow roots see a greater chance of falling over, blocking roads and potentially hitting houses in the process.

2014's Hurricane Arthur peaked at a Category 2, making landfall in North Carolina in early July and leaving more than 40,000 citizens without power.

Category 3 Hurricane

In the event of a Category 3 hurricane, the Saffir-Simpson scale goes beyond the "dangerous" label for wind damage and refers to the effects of the 111-129 mph winds as "devastating." Roofs are at major risk of damage. Trees are likely to be completely uprooted. Electricity could be gone for months, and water could be unavailable to victims for extended periods as well, contaminated with debris. Coastal properties are at a severe risk of damage due to the debris being scattered.

2004's Hurricane Jeanne began to make landfall in Florida when it was still at its Category 3 peak. Millions of Floridians were left without power in its wake.

Category 4 Hurricane

A Category 4 hurricane has a wind range of 130-156 mph according to the Saffir-Simpson scale, and the results of this can be catastrophic. Even well-constructed houses on solid foundation can be destroyed in the wake of a Category 4. It's more likely for a tree to be uprooted than left standing, and they're likely to knock down power poles. Beaches can get massively eroded in all the flooding, electricity and water could be unavailable for months, and whole towns can be completely uninhabitable for long stretches afterward.

The most recent example of the devastation of a Category 4 hurricane was 2017's Hurricane Harvey, which was still at a Category 4 when it struck and then lingered in Houston, TX.

Category 5 Hurricane

Category 5 is the most disastrous level of hurricane on the Saffir-Simpson scale, anything above 156 mph. The combination of pouring rain and gusting wind can cause roofs to collapse entirely. Houses are wrecked as areas become uninhabitable in their flooding. Houses near the coast can be completely washed away.

The most extreme hurricanes of recent memory have been Category 5. In 2017, Puerto Rico, among other islands in Central America, was hit by two Category 5s, Hurricane Irma and Hurricane Maria, in rapid succession. Thousands of citizens died, and it took nearly a full year to restore power.

Hurricane Katrina, the 2005 hurricane that devastated New Orleans, was a Category 5 as well. The damage from the hurricane broke through levees and flood walls which, combined with the unprepared response of the government that drew considerable criticism, led to a reconstruction effort that lasted years.

Is There a Category 6 Hurricane?

The Saffir-Simpson scale does not have any degrees of severity beyond Category 5. However, people have written wondering if the creation of an additional Category 6 is necessary. Category 5 is when a hurricane has winds of 157 mph or more. 2015's Hurricane Patricia, at its peak, sustained a wind speed of 215 mph.

There's a lot of difference between 157 mph and 215 mph, but it has not yet been deemed enough to create a Category 6 hurricane yet.

What Category Hurricane Will Florence Be?

At the moment, Hurricane Florence has strengthened back to a Category 4 hurricane. As it continues to strengthen, some meteorologists suspect it could turn into a Category 5. Washington, D.C. is the latest to declare a state of emergency as it approaches.