Slightly warmer than normal temperatures are forecast across portions of the Pacific Northwest, Great Basin, Rockies, Intermountain West, and west Texas during the month of September. A monthly surplus of late-season cooling degree days of between 20 and 60 is projected throughout these regions of the United States.
Energy costs with respect to cooling may also trend at least slightly higher than average across these parts of the country. Much of the central and eastern United States is likely to see temperatures that on a whole average closer to normal in September as there is still a possibility of the NAO (North Atlantic Oscillation) becoming negative over the next month or two, which can help to establish a cooler weather pattern over the eastern half of the United States at times.
The ENSO phase in the equatorial Pacific remains neutral, but long-range climate models are still indicating about a 65 to 70 percent chance of an El Nino developing during the upcoming fall and winter, which certainly could affect temperatures in the months to come. The timing and strength of this El Nino will continue to be monitored.