After warmest December on record, new year to bring new cooler days

Happy New Year! With the turn of the calendar, this week’s weather also is turning a corner to cooler more seasonable conditions after the warmest December on record.

The average daily temperatures in December for Seattle-Tacoma International Airport (SeaTac Airport) and Bellingham were about 3.5 degrees warmer than average – for the whole month. And if that was not impressive enough, Olympia was just over 6.5 degrees warmer, and on the coast, Forks was seven degrees warmer than normal.

SeaTac Airport and Olympia both averaged 45.5 degrees for the entire month, breaking the previous warmest mean temperatures for December of 45.3 degrees at SeaTac Airport in 2014, and 45 degrees at Olympia established in 1950. Forks crushed its previous record of 44.5 degrees set in 2014 by averaging 48 degrees all month.

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The warm December was sad news for mountain snow enthusiasts. Perhaps this is understating things, but it has been a slow start to the mountain snow season. As of Jan. 1, the Northwest Avalanche Center reported Cascade Mountain snow depths ranged from 33 to 62 percent of normal. And the Natural Resources Conservation Service reported the water in that snowpack was running a paltry 30-to-60 percent of normal for this time of year.

Yet for those who are mountain snow-starved, some good news is in store as the new year gets underway. A change in the weather pattern will result in a series of Pacific weather systems moving inland this week. The first arrives Tuesday with snow levels around 3,500 feet. The next ones roll onshore later in the week and by this weekend, snow levels will tumble between 1,000 and 2,000 feet. For motorists as the week proceeds, be prepared for winter weather driving conditions, particularly by the weekend.

For the rest of Western Washington, rain will return with temperatures much more seasonable for early January, with highs in the mid- and upper-40s this week. Low temperatures will be on either side of 40 degrees.

But by this weekend, cooler air pouring onshore from the Gulf of Alaska will not only drop mountain snow levels, but also decrease lowland temperatures another five degrees or so. In Whatcom and Skagit counties, snowflakes may be seen, and foothill locations may also see some sticking snow.

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Looking ahead toward the middle of January, the cooler weather pattern is likely to continue. So with a record warm December in the rearview mirror, cooler more seasonable January weather is in store for the next couple of weeks.

Ted Buehner is the KIRO Newsradio meteorologist. You can read more of Ted’s stories here and follow him on X, formerly known as Twitter.