… When heavy rain falls, it can overwhelm streams and streets with little to no warning, both along the coast and inland. All it takes is six inches of fast-moving water to knock over an adult, according to the National Weather Service, and most cars can be swept away in as little as a foot of water. Beyond the risk of drowning, floodwaters are often full of sewage, medical waste, industrial chemicals and more. And even after the storm is over, many hazards can remain. … Preparation is key, including heeding evacuation orders and having at least five days of supplies in your home so you can avoid venturing out.