On August 14, the Climate Prediction Center announced conditions now slightly favor La Niña development this fall, with a likelihood under 60%. If the phenomenon forms, cooler-than-average Pacific Ocean waters along the equator could trigger a wetter, colder winter across the northern U.S.-boosting mountain snowpack and irrigation supplies.

For agriculture, that could mean a reversal of some of the severe moisture deficits plaguing the Northwest, where 95% of Washington, 86% of Idaho, and more than half of Oregon are in drought.

Uncertainty Remains

La Niña is far from guaranteed, and even when it develops, outcomes vary. Last winter's La Niña failed to deliver substantial snowpack in Washington, despite early optimism.

Meteorologists analyzed 24 climate models, most of which agree that any upcoming La Niña will likely be weak and short-lived. Neutral ocean conditions are nearly as likely, while an El Niño-which tends to bring warm, dry winters to the Northwest-has a low probability.

Drought by the Numbers

According to the U.S. Drought Monitor, Washington's hardest-hit regions include Asotin, Garfield, Whitman, Chelan, and Okanogan counties. Idaho's driest areas span the Panhandle and southern counties like Twin Falls and Cassia. Overall, 65% of the western U.S. is in some degree of drought.

The third-driest April-to-July period on record in Washington has left rivers running unusually low, the National Centers for Environmental Information reports. Weekend rain is forecast from August 15-17, which could aid fish populations and reduce wildfire risk-but won't erase months of deficits.

Prolonged Dry Periods Pose Challenge

"Long dry spells make it easier to slip into drought and harder to get out of it," said Matt Warbritton, hydrologist with the Natural Resources Conservation Service.

State climatologist deputy Karin Bumbaco says she's "cautiously optimistic" that La Niña could start the path to recovery this winter: "We might see more precipitation and begin drought recovery."