California is known for some beautiful, picturesque weather. But it’s also known for its scary climate, including wildfires and earthquakes. And now, residents need to worry about a new one: Mega floods.

According to a new study by scientists from UCLA and the National Center for Atmospheric Research, the climate change we’re experiencing is severely increasing the risk of disastrous floods, specifically in California. These floods could be so brutal that they could literally leave major cities, such as Los Angeles, completely submerged under water.

The study found that an extreme rainstorm lasting a month or longer could bring more than 100 inches of rain in some areas stretched out through miles across the state.

The problem is that climate change makes these kinds of huge floods almost twice as likely to occur. And when floods take place in warmer climates, “the storm sequence is bigger in almost every respect,” noted Daniel Swain, UCLA climate scientist and co-author of the study, in a news release. “There’s more rain overall, more intense rainfall on an hourly basis and stronger wind.”

It wouldn’t be the first time extreme weather like this has occurred in California, and now global warming is only increasing the chance of a record-breaking flood coming soon.

One of the most noted floods in California was the Great Flood of 1862, which was occurred 300 miles long and 60 miles across the state. On top of putting cities under water, if that flood were to happen now—which is in the realm of possibility—it would cause up to 10 million people to become displaced, shut down major freeways for or months at a time and many more catastrophic outcomes.

“Parts of cities such as Sacramento, Stockton, Fresno and Los Angeles would be under water even with today’s extensive collection of reservoirs, levees and bypasses. It is estimated that it would be a $1 trillion disaster, larger than any in world history,” the study states.

So what now? More research needs to be completed, including the proper ways to respond to this kind of situation. The California Department of Water Resources are hoping to introduce advances such as types of flood simulations to help. Additionally, researchers are hoping to be able to map out where flooding could be the worst, which will help in planning.

Learn more about the study, published in peer-reviewed journal Science Advances, a publication of the American Association for the Advancement of Science, here!