NOAA's Climate Prediction Center says a majority of models are now predicting that La Niña conditions will emerge this fall, from September to November, and continue through January.
A July 8 discussion says La Niña now has a 66 percent chance of occurring from November to January. Models also say ENSO-neutral conditions are favored through the summer and into fall, with a 51 percent chance of remaining ENSO-neutral from August to October. ENSO stands for El Niño-Southern Oscillation.
Predictions are based partly on sea surface temperatures in a specific location of the Pacific Ocean along the equator, which have remained close to average.
La Niña occurs when sea surface temperatures are 0.5 C (0.9 F) or more below average, and when the atmospheric conditions in the Pacific Ocean respond to the cooler sea surface temperatures.
Last winter, La Niña emerged in September and remained in place through the winter. Prior to last winter, the winter of 2017-2018 was the most recent La Niña winter.
In the West, La Niña winters bring a greater chance for cooler and wetter weather in the Pacific Northwest. California is typically in a transition zone, with wetter than normal conditions more likely in Northern California and drier than normal conditions more likely in Southern California.
Lower temperatures would increase how much time people spend inside, which many epidemiologists believe speeds transmission of COVID-19.
Given the virus's more contagious Delta variant, these factors could yield a resurgence in the pandemic, which in turn could prompt lockdowns and other public health measures, Chris Ellinghaus, energy analyst with Siebert Williams Shank, wrote in a July 12 research brief.
"Should a La Niña develop later this year as it appears it may, electric utility loads could likewise be adversely affected if the cooler temperatures return into mid-2022," Ellinghaus wrote.