MYNORTHWEST WEATHER

Seattle winter may come sooner than you think

Nov 27, 2023, 11:32 AM | Updated: Nov 28, 2023, 8:40 am

Snow piles up on a street as a car maneuvers down the street in Seattle last year. (AP Photo/Elaine...

Snow piles up on a street as a car maneuvers down the street in Seattle last year. (AP Photo/Elaine Thompson, File)

(AP Photo/Elaine Thompson, File)

Meteorological winter starts on Friday, Dec. 1, but winter as we know it begins on the solstice — this year on Dec. 21 around 7:30 p.m. in Seattle. Why the difference in when winter begins?

Astronomical Seasons

The winter solstice, the shortest day of the year in the Northern Hemisphere, is based upon astronomical seasons that people have used to mark time for thousands of years. For the Southern Hemisphere, Dec. 21 is the summer solstice and longest day of the year.

Astronomical seasons are based upon the position of Earth as the planet rotates around the sun. Earth’s 23.5-degree tilt and the sun’s alignment over the equator determine both the winter and summer solstices and equinoxes. The equinoxes mark the time when the sun is centered above the equator, around March 21 for the spring equinox and around Sept. 21 for the autumnal equinox.

Meteorological Seasons

Many think of winter as the coldest time of the year and summer as the warmest, with spring and fall being the transition seasons. This is the basis for meteorological seasons. Meteorologists and climatologists break the seasons into groups of three months based on the annual temperature cycle combined with the calendar.

The coldest months of the year are December, January and February, and hence determine meteorological winter.

More from Ted Buehner: Seattle weather sunny to start the week, but rain is on the way

In addition, the length of meteorological seasons is also more consistent by following the calendar. The calendar makes it much easier to calculate seasonal statistics from monthly weather data versus astronomical seasons — very useful for commerce, agriculture and a variety of other needs.

And speaking of the calendar, as December begins so does typical Pacific Northwest winter weather. Right on cue, rain and blustery conditions will resume in Western Washington, and snow begins piling up in the mountains, with snow levels generally below highway pass levels. So buckle up. After this period of unusually cool, dry, locally foggy, and sunny November weather, winter conditions return.

Back to astronomical versus meteorological seasons! In summary, astronomical seasons are based on the position of Earth in relation to the sun while meteorological seasons are based upon the annual temperature cycle and the calendar. And now you are ready for that trivia question!

Follow Ted Buehner, the KIRO FM news meteorologist, on Twitter 

MyNorthwest Weather

Warmer temperatures recently brought people out to Green Lake....

Ted Buehner

Winter’s still here, but the weather will reflect a sense spring is coming

It is mid-February. Each day is getting a bit over three minutes longer and daylight hours have expanded to about 10.5 hours.

1 day ago

Windstorm...

Bill Kaczaraba

Windstorm coming to Western Washington

A windstorm is coming to Western Washington on Friday night through Saturday, the National Weather Service (NWS) reports.

4 days ago

snowpack, levels...

Ted Buehner

Mountain snowpack sending major warnings about water supplies

It’s the middle of February and Washington's mountain snowpack is well below average from where it should be.

5 days ago

western washington snow...

Frank Sumrall

Parts of Western Washington see slush and snow, most schools delayed or closed

According to KIRO 7, we will have some wet snow mixing in with rain at times, but for the most part, we’ll see just wet roads into Thursday morning.

5 days ago

washington snowpack...

Frank Sumrall

Cliff Mass on state’s depleted snowpack: ‘We understand … it’s not climate change’

UW atmospheric science professor Cliff Mass cited the region's El Niño winter conditions as the most significant reason for the depleted snowpack. 

7 days ago

Sunbreak...

Ted Buehner

Who do we share the term ‘sunbreak’ with?

Where did the term sunbreak originate and who does the Northwest share it with?

9 days ago

Seattle winter may come sooner than you think