Global warming is happening now and its effects are being felt in the United States and around the world. Among the expected consequences of global warming is an increase in the heaviest rain and snow storms, fueled by increased evaporation and the ability of a warmer atmosphere to hold more moisture. An analysis of more than 80 million daily precipitation records from across the contiguous United States reveals that intense rainstorms and snowstorms have already become more frequent and more severe. Extreme downpours are now happening 30 percent more often nationwide than in 1948. In other words, large rain or snowstorms that happened once every 12 months, on average, in the middle of the 20th century now happen every nine months. Moreover, the largest annual storms now produce 10 percent more precipitation, on average. An increase in extreme downpours has costly ramifications for the United States, with the potential to cause more flooding that jeopardizes property and lives. With scientists predicting even greater increases in extreme precipitation in the years ahead, the United States and the world must take action to reduce pollution that contributes to global warming.