 That can cause severe damage to homes, tear off roofs, knock down trees. But the most dangerous threat is often water and flooding. For coastal communities, a big risk is from storm surges, essentially walls of water that get pushed onshore. Rain is also a growing threat. Warmer air can hold more moisture. So really big hurricanes can hold a lot of water vapor that comes down as torrential rain. That can threaten inland communities that might not be right in the path of the storm.