Image (click to enlarge): 500 mb height at 8 am EDT, Sept. 22 For other record temperature posts, see: 
Record Heat 
Record ColdSept. 23 Update: Additional record reports:
Roseburg OR 101°, broke 1994 record of 100°
Montague CA 95°, tied 1974 record
6 PM PDT Update: Today's unofficial high at Portland was 92°.  Other Oregon and Washington highs in the 90s: 
Kelso     93°
Scappoose 92°
Vancouver 93°
Astoria   92°
Bremerton 93°
Ft. Lewis 91° 
Preliminary National Weather Service record reports released so far: 
A RECORD HIGH TEMPERATURE OF 92 DEGREES WAS SET AT ASTORIA OR TODAY.   
THIS BREAKS THE OLD RECORD OF 89 SET IN 1989.  
AS OF 3 PM PDT...PORTLAND AIRPORT REACHED 91 DEGREES. THIS SETS A NEW   
RECORD OF 24 DAYS THIS YEAR THAT EXCEEDED 90 DEGREES. THE PREVIOUS   
RECORD OF 23 DAYS WAS SET IN 1987.    
3 PM PDT Update: The Portland temperature of 91° makes this the 24th day of the year at 90°+ and sets a new record.  The reading of 92° at Astoria breaks the record of 89° for the date set in 1989 and is the latest 90° temperature ever recorded there.  The previous latest was 91° on Sept. 13, 1957.  The previous latest 92° temperature was on Sept. 4, 1955.
PM Update: At 2 pm PDT, Portland is reporting a temperature of 88°.  Astoria, on the coast, is at 91°, and Kelso, Washington is 90°.
Original post:A very strong upper-level ridge of high pressure is helping to extend this summer's record heat into the fall in the Pacific Northwest.  In anticipation of a much-above-average high in the low 90s in Portland, the National Weather Service has issued a statement reviewing heat statistics for northwest Oregon.  A high of 90° or above would break the record annual number of 90° days of 23.  The high yesterday was 85°.  As of noon PDT, the temperature is 83°, up 14° in 2 hours.  
PERIOD OF RECORD: 
PORTLAND...1940-CURRENT 
SALEM......1892-CURRENT 
EUGENE.....1890-CURRENT 
********************************************************* 
AVERAGE NUMBER OF DAYS PER YEAR: 
                        PORTLAND      SALEM       EUGENE 
90 DEGREES OR ABOVE.....    11           15          11  
100 DEGREES OR ABOVE....LESS THAN 1   ABOUT 1    LESS THAN 1 
********************************************************** 
NUMBER OF DAYS SO FAR THIS YEAR (2009): 
                        PORTLAND      SALEM       EUGENE  
90 DEGREES OR ABOVE.....    23           22          20  
100 DEGREES OR ABOVE....    3            3           4 
********************************************************** 
RECORD TOTAL NUMBER OF DAYS IN A YEAR: 
                        PORTLAND      SALEM       EUGENE 
90 DEGREES OR ABOVE.....  23/2009     34/1958      31/1958 
               NOTE....PORTLAND TIES RECORD SET IN 1987.  
100 DEGREES OR ABOVE....   5/1977     7/1988       5/1978 
********************************************************** 
RECORD NUMBER OF CONSECUTIVE DAYS OF HIGH TEMPERATURES  
FOR THE ENTIRE YEAR: 
                        
90 DEGREES OR ABOVE.....RANK  #DAYS   START DATE 
FOR PORTLAND............ 1.   10      7-25-2009   
                        2.    8      8-12-1967  
                        3.    7      8-03-1972 
                        4.    7      9-04-1944 
                        5.    6      7-22-1996 
                         
FOR SALEM............... 1.   10      8-11-1967 
                        2.   10      7-13-1938 
                        3.    9      7-25-2009   
                        4.    9      8-05-1977 
                        5.    9      7-27-1974 
                         
FOR EUGENE.............. 1.   11      7-13-1938 
                        2.   10      7-26-1974 
                        3.   10      8-11-1967 
                        4.    9      8-03-1990 
                        5.    9      7-21-1939 
100 DEGREES OR ABOVE....RANK  #DAYS   START DATE 
FOR PORTLAND............ 1.    5      7-13-1941             
                        2.    4      8-07-1981 
                        3.    3      7-25-2009                 
                        4.    3      7-19-1994               
                        5.    3      8-10-1977                 
                         
FOR SALEM............... 1.    4      7-19-1994  
                        2.    4      8-07-1981  
                        3.    4      8-09-1977  
                        4.    4      7-13-1941  
                        5.    3      7-25-2009    
FOR EUGENE.............. 1.    4      8-07-1981 
                        2.    3      7-25-2009      
                        3.    3      7-22-2006               
                        4.    3      8-10-1977              
                        5.    3      7-22-1928     
In the interior of Washington and Idaho, high temperature records are expected to be threatened on Wednesday, Sept. 23: 
HIGH TEMPERATURES ARE PROJECTED TO BE 10 TO 20 DEGREES ABOVE NORMAL  
WEDNESDAY. SOME RECORDS FOR THE AREA ARE LISTED BELOW ALONG WITH  
FORECASTED TEMPERATURES. 
                 ...WEDNESDAY 9/23/2009.... 
       STATION        FORECAST    RECORD (YEAR) 
       BONNERS FERRY   90          85    (1987) 
       BOUNDARY DAM    89          83    (1987) 
       CHELAN          89          87    (1987) 
       COEUR D'ALENE   89          93    (1966) 
       COLVILLE        92          94    (2001) 
       CONCONULLY      89          87    (1987) 
       DEER PARK       90          90    (2001) 
       ENTIAT          94          89    (1999) 
       EPHRATA         90          92    (1987) 
       FELTS FIELD     91          91    (2001) 
       LEWISTON        95          97    (2001) 
       MAZAMA          91          89    (1987) 
       OMAK            92          89    (1939) 
       PLAIN           88          88    (1990) 
       PORTHILL        88          86    (1999) 
       POTLATCH        95          93    (1938) 
       PRIEST RAPIDS   91          90    (1999) 
       PULLMAN         92          93    (1987) 
       REPUBLIC        90          92    (1928) 
       SANDPOINT       86          83    (1987) 
       SPOKANE         89          91    (1905) 
       WELLPINIT       92          91    (1987) 
       WENATCHEE WATER 93          90    (1939) 
       WENATCHEE       90          90    (1974) 
       WINTHROP        91          91    (1987)