SEATTLE TACOMA INTL AP, WASHINGTON

Period of Record General Climate Summary - Heating Degree Days

Station:(457473) SEATTLE TCOMA WSCMO AP
From Year=1948 To Year=2012
Heating Degree Days for Selected Base Temperature (F)
Base	Jan.	Feb.	Mar.	Apr.	May	Jun.	Jul.	Aug.	Sep.	Oct.	Nov.	Dec.	Annual
65	773	627	615	470	306	159	60	55	151	392	600	755	4964
60	618	486	460	322	168	54	7	6	51	240	450	600	3462
57	525	401	368	237	99	18	1	1	19	157	361	507	2693
55	463	345	306	183	62	7	0	0	8	110	301	445	2230
50	310	208	162	68	10	0	0	0	1	31	165	293	1249

Heating Degree Day units are computed as the difference between the base temperature and the daily average temperature. (Base Temp. - Daily Ave. Temp.) One unit is accumulated for each degree Fahrenheit the average temperature is below the base temperature. Negative numbers are discarded. Example: If the days high temperature was 65 and the low temperature was 31, the base 50 heating degree day units is 50 - ((65 + 31) / 2) = 2. This is done for each day of the month and summed.
Table updated on Oct 31, 2012
Months with 5 or more missing days are not considered
Years with 1 or more missing months are not considered

Western Regional Climate Center, wrcc@dri.edu