Oregon Chapter
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Past Weather

December 14, 2009


December 2009 Arctic Blast

Steve Pierce
Oregon AMS
stevejpierce@comcast.net

Headlines: 
Coldest Four Consecutive Overnight Low Temperatures in Portland Airport History, this early in the season!

During the first week of December 2009, an air mass originating in the arctic slid south across the Pacific Northwest bringing with it record breaking overnight low temperatures. Temperatures west of the Cascades fell as low as the single digits at some reporting stations and to as low as -25 degrees east of the Cascades. This cold spell also marked the coldest overnight low temperature in more than 11 years in Portland. As mentioned above, it also marked the coldest four consecutive overnight low temperatures (13.25 degrees when averaged from 12/8 to 12/11) in Portland airport history, this early in the season. This barely edges out the exact same timeframe in 1972 (12/8/72 to 12/11/72 averaged 13.75 degrees). Records have been kept at PDX since 1940! 

Here are some of the highlights -

Coldest of the December 2009 overnight lows at PDX

12/4/09     25        12/9/09     12
12/5/09     27        12/10/09   13
12/6/09     28        12/11/09   14
12/7/09     23        12/12/09   30
12/8/09     14

PDX's Top 10 coldest December nights (1940-2009) as measured at the Airport (PDX) ---

12/16/1964      6         12/18/1964     11
12/17/1964      7         12/23/1998     11
12/30/1968      8         12/23/1983     12
12/8/1972        8         12/21/1990     12
12/31/1968      9         12/9/2009       12

Did you know ---

There are just under 25,000 calendar days of records at PDX from 1941-2009. Only 42 of those days featured low temps colder than what PDX recorded during this outbreak. Finally, PDX has not been below 10 degrees for an overnight low since Feb 1989, over 20 years ago.