"The odds favor a hotter than average summer for much of the Western U.S., and a closer to average one for the Eastern U.S., according to the May seasonal forecasts from The Weather Company’s WSI branch, and Columbia University’s International Research Institute for Climate and Society (IRI). Meteorological summer began on June 1, and the first week of summer has been on the cool side for much of the United States. However, a shift in the jet stream pattern is coming late this week and into early next week, which will bring hot conditions to much of the eastern half of the U.S. WSI anticipates the possibility of a weak El Nino late summer, perhaps with enough influence on the tropical atmosphere to limit the magnitude of the heat across the northern Plains, Great Lakes, and Eastern U.S. Similarly, in an outlook issued in mid-May, a model-based outlook from IRI and NOAA gave slightly-better-than-even odds of El Niño developing. However, the offiical NOAA/IRI forecast from early May has lower odds, between 40% and 50%. If El Niño does not develop, the odds of stronger and more widespread U.S. heat this summer will rise."

"NOAA is predicting increased odds of a hot summer not only for the Western U.S., but also for the South and Northeast. WSI also predicts a hot summer for the Southeast during July and August. So, what does this mean for air pollution levels this summer?"