Sea-surface temperatures across the equatorial Pacific Ocean are still showing signs of El Nino trying to develop. Much of the central and western equatorial Pacific has water temperatures that are 1 to 2 degrees warmer than average. The climate models suggest that a neutral or weak El Nino phase will be in place during the upcoming winter months; meaning warmer than normal December temperatures for portions of the Pacific Northwest, north-central Rockies, Great Basin and northern Plains.
Total heating degree-days for the month might be lower than average by between 30 and 90 throughout much of these regions of the country. Heating costs are projected to be lower than average; however, cooler than normal temperatures are forecast for parts of the Midwest, Mid-Atlantic, Northeast and Southeast. A big factor in the eastern third of the country is the NAO (North Atlantic Oscillation), especially during winter. The NAO has been negative for much of the past few months and indications are saying this trend will continue through late November into at least early December. This would favor a colder than normal weather pattern across the eastern United States.
If El Nino further develops, wetter and cooler conditions might become more frequent across the Southeast. A surplus of heating degree-days, as well as higher heating costs, can be expected in these regions during December.