On Monday (September 10), 1.5 million people were ordered to evacuate as Virginia and the Carolinas prepare for Hurricane Florence. If the storm makes landfall as a Category 4 hurricane (meaning it has winds of 130 to 156 mph), it will only be the third recorded storm to do so along the eastern coast of the United States. As unprecedented as this is, climate change could make Florence’s strength the future norm.  

According to a number of scientists and meteorologists, there are two major ways that climate change factors into dangerous consequences for the intensity of the hurricane. The first factor, reports NPR, is that climate change causes the wind currents that hurricanes ride to slow down. It is predicted that Florence will nearly stall once it makes landfall, becoming like a “faulty sprinkler,” says NPR, “stuck watering one area for days on end.” Reports The Atlantic:

While Florence is parked, it could unload up to 32 inches of rain onto parts of North Carolina and Virginia, which usually only see around 40 to 50 inches in a given year.

This halt-and-downpour scenario is reminiscent of what Houston faced last summer, and a pattern that will only get more likely as the world warms. During Hurricane Harvey, urban sprawl and an abundance of impermeable ground cover made it difficult for the torrential downpour, once dumped, to exit the city. In the Southeast, according to Konrad, steep hillsides and already waterlogged soil will similarly fail to absorb much of the rain Florence will bring.

The second way that climate change affects hurricanes is that global warming increases ocean temperatures. Per NPR:

“We have global warming, and so this actually makes these storms bigger and more intense,” [Kevin Trenberth of the National Center for Atmospheric Research] explains. Humans burn fossil fuels in our cars, our power plants and our airplanes, all of which release greenhouse gases, which trap heat. Warmer oceans, especially, provide fuel for hurricanes in the form of evaporating moisture.

“The oceans are warmer now than they’ve ever been, and they’re going steadily upwards,” Trenberth explains. In a study published in May, he and colleagues found rain from Hurricane Harvey was powered by the highest ocean temperatures ever recorded in the Gulf of Mexico.

Right now, the part of the Atlantic under Florence is slightly warmer than usual, and the area north of the storm is significantly above normal, he says.

Coastal communities in Florence’s path are in the most danger of flooding. And in the United States, coastal communities are disproportionately occupied by people of color.

In addition to geography, communities of color also are affected more seriously by the mental health consequences of hurricanes. A 2017 report from the American Psychological Association, in partnership with Climate for Health and ecoAmerica, found that changes in weather—many exacerbated by climate change—negatively impacts the mental health of those experiencing it. Communities of color feel the brunt of the symptoms—including PTSD, stress and anxiety—more than others, researchers said. Survivors of natural disasters like hurricanes were likely to suffer both immediate and long-term health impacts

Florence is predicted to make landfall along the North Carolina-South Carolina border on Thursday or Friday, with winds close to 155 miles per hour.