Blame El Nino, the periodic Pacific weather phenomenon that has been disrupting weather worldwide.
Federal forecasters predicted Thursday that it will continue through spring before easing back toward more normal conditions.
The El Nino phenomenon has reached its mature stage, the National Weather Service said in its monthly update.
The agency's Climate Prediction Center said sea surface temperatures in the equatorial Pacific Ocean remained more than 2 degrees Fahrenheit above average in December. Temperatures below the surface were above normal in the eastern Pacific, while cold subsurface temperatures were recorded in the western equatorial Pacific.
"These sea-surface temperatures indicate the mature phase of El Nino is in place," said center director Jim Laver. El Nino occurs when sea-surface temperatures in the equatorial Pacific Ocean remain above average for more than several months.
This can affect the atmosphere above the ocean, disrupting the powerful winds that steer weather patterns and potentially affecting weather around the world.
"Typically, El Nino impacts on the U.S. are strongest during the winter and early spring due to changes in the jet stream, and the pattern of storm activity," said Vernon Kousky, lead El Nino forecaster. He added this El Nino will continue to remain weaker than the strong 1997-98 version.
The forecasters say El Nino is likely to continue producing drier-than-average conditions around the Ohio Valley states and northern Rockies; wetter-than-average conditions along much of the southern tier of the nation; and warmer-than-average temperatures across the northern tier states and southern and southeastern Alaska.
Storms in recent weeks have helped ease drought conditions along the Gulf Coast and Southeast from Texas through Georgia, though some interior areas remain dry.
The precipitation has restored many wells and reservoirs in the East to near normal levels, with some even above-normal.
Rain and snow storms have battered California. The snow pack has increased to above-normal levels there, but drought conditions remain throughout sections of the interior West and Great Plains.
Drought has continued with little improvement in most of Montana, Wyoming, Utah, Nevada, Arizona and New Mexico, the Weather Service said. Colorado has experienced early season snows, but much more is needed for significant drought relief, Laver said.
In addition, there has been below-normal rain and snow for the past few months in North and South Dakota and Nebraska and there has been little relief for drought-weary sections of Missouri and Kansas. Drought conditions extend from Michigan into southern Iowa, and could expand both northward and southward in coming months.
El Ninos occur every three years to seven years with the ocean returning to more normal temperatures in between. Sometimes an unusually cool condition called La Nina can occur, which also affects the weather.
While forecasters cannot predict these events months in advance, in the past El Ninos tended to be first noticed around Christmas, when South American fishermen would see a sudden decline in the fish crop. Because of the timing the named the event El Nino,
Spanish for "little boy" and a term also used for the Baby Jesus.
The weather service is a division of the Commerce Department's National Oceanic and Atmospheric Administration.
By Randolph E. Schmid