SEATTLE – The weather in Western Washington may already be feeling a little like winter, but it doesn’t officially begin until Saturday, Dec. 21.

The winter solstice is at 1:20 a.m. PST. It is the official start of winter and the shortest day and longest night of the year.

There will be less than 12 hours of daylight in the Northern Hemisphere.

During the solstice, the sun is at its lowest point in the sky during the year, according to NASA, because the northern half of the Earth is tilted furthest away from the sun due to the planet’s axis. Meanwhile, people south of the equator are experiencing the longest day of the year – the summer solstice.

After the solstice, the days slowly become longer.

According to the National Weather Service Climate Prediction Center, La Niña conditions are most likely to occur through January. However, the chances have decreased.

In September, the weather service reported a 74% chance of La Niña for November through January. According to the latest forecasts, the probability is only 59%.

During a La Niña weather pattern, trade winds strengthen along the equator, displacing warm seawater from Peru, which is then replaced by colder water. This will push the jet stream further north, keeping the southwestern parts of the U.S. drier and the northwest cooler and possibly wetter.

There have been 25 La Niña patterns since 1954. Only seven of them were considered strong.

Over a period of 25.14 years, temperatures in Seattle fell below normal, with the average temperature being just 2 degrees cooler than normal.

Precipitation varied more, with a split of about half above normal and half below normal in Seattle.

Snow amounts in Seattle have typically been higher than normal during La Niña winters. Typical for the season is 5 inches, but the 25 La Niña winters averaged 11.5 inches per year. It should be noted that some anomaly years influence this average, including the 63.6 inches of snow that fell in the winter of 1949–1950.

An El Niño pattern is the opposite of La Niña, when trade winds weaken and warm water remains to the east and collects off the coast of Peru. That impacts the jet stream, which is essentially a path that pushes storms along the United States. The warm water pushes the jet stream south, driving storms into the southwestern parts of the country, while the northwest remains warmer and typically drier.

El Niño and La Niña are phases of the El Niño Southern Oscillation, which measures sea surface temperatures in the central Pacific.

According to the United States Department of Agriculture, snowpack conditions at the Olympics and in the Southern Cascades are near or above average.

The situation is different in the central and northern Cascades, where snowpack is slightly below normal.