Here Are The Coldest Days Of The Year In Puget Sound

SEATTLE — Climatologists with the National Oceanic and Atmospheric Administration have released a new interactive map showing the average coldest day of the year at monitoring stations across the United States, updated to reflect the latest climate normals through 2020.

There is good news for Western Washington: For most of us, that day has already come and gone. However, a few factors can still make for a late-season surprise, and Puget Sound is no stranger to a February snowstorm.

Here are a few coldest days around Puget Sound (1991-2020 averages):

• Seattle (Sand Point)
  • Coldest day: Dec. 23
  • Average temperature: 36.5°
• Renton
  • Coldest day: Dec. 20
  • Average temperature: 36.3°
• Tacoma
  • Coldest day: Dec. 20
  • Average temperature: 36.5°
• South Hill (McMillin Reservoir)
  • Coldest day: Dec. 19
  • Average temperature: 32.6°
• Snoqualmie Falls
  • Coldest day: Feb. 15
  • Average temperature: 35.1°

Generally, the West tends to see its coldest days in December, while the Midwest and East are more likely to reach their minimum temperatures in January or later. Mountain ranges also play a role in creating pockets where some communities see their coldest days later than their neighbors.

"In the West, the coldest day of the year usually occurs in December," NOAA explains. "Islands of late-winter dates are often valleys where temperature inversions allow air to keep cooling even after the coldest day in the surrounding area has typically passed. In the East, the coldest day of the year is typically later in the season thanks to cold air from the snow-covered parts of Canada dipping down into the area."

NOAA researchers found that Eastern states experienced a more uniform change since 2010, while trends in the West are more of a mixed bag.

"Compared to the 1981-2010 version of this map, there has been a small but noticeable shift of the coldest day to dates 3–6 days later or more at many stations in the U.S. east of the Rocky Mountains," NOAA writes. "This is not surprising given that early winter warming is more pronounced than late winter warming between the new and previous Normals periods in this region. While the far northwestern U.S. also shows a shift of the coldest day to a later time, the rest of the western U.S. does not show a consistent pattern, with some stations actually shifting to earlier coldest day times."

View an interactive map charting the coldest days of the year on NOAA's website.

NOAA said its temperature normals can guide long-term planning for economic sectors, helping energy companies predict peak energy demand and construction and tourism industries plot out their seasons. While the 30-year averages help paint a broad picture, there is plenty of room for seasonal deviations and climate patterns like La Niña.

During last month's cold snap, the National Weather Service recorded Seattle's coldest day in more than three decades, with a high of just 23 degrees on Dec. 27. Looking ahead, the Climate Prediction Center's latest seasonal outlook places good odds on temperatures landing below average in Washington between February and April.