An anonymous reader quotes a report from UCAR.edu: The formation of a distinct pattern of sea surface temperatures in the middle of the North Pacific Ocean can predict an increased chance of summertime heat waves in the eastern half of the United States up to 50 days in advance, according to a new study led by a scientist at the National Center for Atmospheric Research (NCAR). The pattern is a contrast of warmer-than-average water butting up against cooler-than-average seas. When it appears, the odds that extreme heat will strike during a particular week -- or even on a particular day -- can more than triple, depending on how well-formed the pattern is. "We found that we could go back as far as seven weeks and still predict an increase in the odds of future heat waves," said McKinnon, a postdoctoral research at NCAR and the lead author of the study. "What's exciting about this is the potential for long-range predictions of individual heat waves that gives society far more notice than current forecasts."