While the condition marked by cooler-than-normal sea surface temperatures in the tropical Pacific is persisting, the government's Climate Prediction Center said Thursday that some weakening is evident.
La Nina and its opposite, El Nino, change wind and air pressure patterns that can affect weather around the world.
This winter La Nina dominated the flow coming off the Pacific, moving storms through the Ohio Valley and with heavy precipitation to the Great Lakes and the East.
The center said current wind and pressure patterns over the Pacific "reflect an ongoing and mature La Nina that has begun to weaken."
Some computer climate models predict neutral conditions between La Nina and El Nino by May through July, while others suggest a continuing-but-mild La Nina.
From now through April, the center said, the weakening conditions suggest the likelihood of above-average precipitation in the Northern Rockies and western regions of the Northern Plains, the Great Lakes and Ohio Valley. Below-average precipitation is likely across much of the Southern states.
Cooler-than-usual temperatures are likely for much of the West Coast and northern tier of states, except New England. Warmer-than-normal readings are expected for the southern and central U.S.