Autumn arrives, wet weather coming

Framed by leaves that are changing to their autumn hue, a boat drifts into a Clarkston boat launch on the Snake River on Tuesday. Fall officially arrives today in the Northern Hemisphere.

Today marks the first day of autumn, and cool, wet weather is in the forecast beginning next month, according to the weather experts.

Jennifer Simmons, a meteorologist at the National Weather Service in Spokane, said October, November and December will likely have average temperatures, but above-normal precipitation is anticipated. A La Niña winter is expected, and those conditions tend to favor more moisture.

The winter forecast may come as a relief after drought conditions and the hottest summer on record remains fresh in our memories. Warm temperatures are expected to continue through this month, but change is coming, Simmons said.

The Lewiston-Clarkston Valley and entire region are expected to experience a La Niña winter, the National Weather Service spokeswoman said.

La Niña is characterized by a shift in weather patterns that occurs every two to seven years, caused by strong westerly trade winds that upwell cooler ocean waters in the eastern Pacific Ocean. The cool waters push the polar jet stream north, bringing colder temperatures, heavy rains and flooding to the Pacific Northwest.

In addition to the change in seasons, the autumnal equinox arrives today at 12:21 p.m. PDT in the Northern Hemisphere, which signals the halfway point between the longest and shortest days of the year. Daylight hours will continue to dwindle until the shortest day of the year, the winter solstice, on Dec. 21.

Also coming during the fall is the end of daylight saving time and the return of standard time Nov. 7.