Sea-surface temperatures remain slightly warmer than average across much of the Equatorial Pacific, although some slight cooling has been observed across the eastern Pacific Ocean in recent weeks. The latest long-range climate models suggest that this weak El Nino will gradually transition to a neutral phase over the next couple months. This neutral phase is then forecast to persist through the fall and likely the upcoming winter season.
As for the September temperature outlook, slightly above normal temperatures are predicated across portions of the northern Rockies, Intermountain West, Desert Southwest, and southern Rockies. A surplus of total monthly cooling degree days of between 20 and 60 is projected across these regions of the country. Also, parts of Florida may see slightly warmer than normal temperatures in September. Much of the central and eastern United States is forecast to see temperatures average closer to normal in September. It should be noted that if the NAO (North Atlantic Oscillation) remains negative over the next few weeks, some parts of the eastern half of the United States could end up being slightly cooler than normal during September, but confidence is not high enough in that solution at this point in time.