It’s sneezing and wheezing season again. Scientists at Columbia University and the National Center for Atmospheric Research in Boulder, Colo., have devised a forecasting method by which they can predict how severely cities will be hit by the flu. So far, they’ve studied New York City, finding that particularly hellish flu epidemics follow periods of very dry weather. Now, whether this is applicable to other cities is a big question. But if it proves accurate, it can help cities stock pile vaccines to combat a disease that kills 35,000 annually in the U.S.