In eastern Kentucky, at least 37 people died in flooding caused by heavy rain. With many residents still unaccounted for, Gov. Andy Beshear (D) said he expects the death toll to rise. The destruction is widespread, and it could take years to repair all of the damaged infrastructure. Here’s everything you need to know:

Why was the flooding so severe?

The rain began overnight on July 30, with up to 10 inches of rain falling in some areas of eastern Kentucky in 24 hours. The ground was so saturated from the torrential downpour that it couldn’t absorb the extra water, leading to flash floods. Rebecca Hersher of NPR’s climate team explains that when the water has nowhere to go, it begins to “pool on the surface. And then if there’s a hill — even a really small hill, one that you might not even notice — all that water starts to roll downhill. It gathers speed, it gathers power, it can pick up debris. And that is a flash flood. It’s really dangerous. It can carry away cars, it can carry away houses, it can kill people.”

Why did so many people die in the flooding?

Kentucky’s state climatologist, Megan Schargorodski, told NBC News that “the biggest danger that came with this flooding is that most of the rain happened very quickly, very heavily, and overnight.” William Haneberg, director of the Kentucky Geological Survey, said eastern Kentucky has “mountainous terrain and the valleys are very narrow. A lot of the areas affected are very remote. It may take you an hour to go through the curving mountain roads. In a lot of the remote areas, there may only be one way out. So if you wait too long, the bridges may be washed out.” Schargorodski agreed, saying that “many routes get blocked due to floodwaters, and it can sometimes actually be more dangerous to evacuate.”

In areas with higher poverty rates, where many people don’t have cars or access to the internet, they might not have known right away about the flooding, or had a way to quickly escape the rising floodwaters. Forecasters were correct in predicting significant rainfall in eastern Kentucky, but it wasn’t known which areas would flood; Schargorodski noted that evacuations can happen a few days before a hurricane hits, but it’s different with a rain storm.

The victims include Gabriel Hensley, a 30-year-old father of five from Perry County who was swept away by floodwaters while trying to help an injured driver, as well as four siblings between the ages of two and eight years old who lived in Knott County. Beshear said the children were swept away by a strong current.

Are there still people missing?

Yes. Beshear said that as of Tuesday, there are hundreds of people across five counties who are unaccounted for, and in some rural areas, there’s no way to know how many residents are missing — cell phone service is down, and the roads and bridges leading to these communities were wiped out by the flooding. That’s also a problem for survivors, who need supplies like food, water, and medicine, but can’t be reached. “I still have aunts and uncles that are stuck in hollers,” Zack Hall, a resident of Knott County, told CNN on Tuesday. “They are diabetics. They need insulin.” Hall said he was able to get to one relative’s home with an ATV, “but there was no road” and the “infrastructure … is just completely destroyed.”

How much damage has been done?

This is “one of the most devastating deadly floods that we have seen in our history,” Beshear said, and it is impacting thousands. The water swept some people miles away, and the governor told CNN it will take weeks to account for the missing and much longer to rebuild the destroyed communities.

The flooding wiped out bridges and roads and took down power lines, and residents are removing water, mud, and debris from their homes and trying to dry out their things. In the small city of Fleming-Neon, the city hall was completely destroyed, and there is a foot of mud covering everything inside the building, CNN reports. The city’s bank, post office, and pharmacy all flooded, and the internet is down. Several schools across the region were also destroyed or heavily damaged, with Kentucky Department of Education spokesperson Toni Tatman telling CNN that some schools will have to delay reopening for the fall.

How can a similar tragedy be avoided in the future?

Climate change is fueling these storms that are bringing heavy rains to Kentucky, Hersher said, and climate scientists say that as humans keep burning fossil fuels, it’s making the atmosphere hotter, so the air holds more moisture and it rains harder. In Kentucky, where heavy rain has increased by almost a third, Hersher said retention ponds can be built to collect excess water. She also said cities can upgrade their stormwater systems, which were built decades ago, to have bigger pipes built for the current climate.

The National Weather Service is also looking into new ways to give people as much time as possible to get to higher ground during a flooding event, Hersher said. As soon as a local office notices heavy rain in an area, they send out a flash flood alert to cell phones.

How can I stay safe in a flash flood?

The American Red Cross says it is important to know the difference between a flash flood watch and a warning — if it’s a watch, it means a flash flood is possible, and if it’s a warning, it means it is already happening or will begin soon.

During a flash flood, move to higher ground if you aren’t already there, and steer clear of low-lying areas. Do not walk into floodwaters; there could be downed power lines, waste, wild animals, and dangerous debris in the water. If you are in a car, do not continue to drive toward the flooding; the Red Cross warns that cars can get swept away by less than two feet of moving water. If you are already on a flooded road and see that the water is rising, get out of your car and get to higher ground. At night, be extra cautious, since it will be harder to see your surroundings. Turn your television or radio to a local station, so you can hear the latest weather information and evacuation orders.