longest day of the year in seattle
Sunshine & Daylight Hours in Seattle, Washington, Usa. 1  The longest day of the year is 15:46 long and the shortest day is 8:13 long. 2  The longest day is 7:33 longer than the shortest day.  There is an average of 2044 hours of sunlight per year (of a possible 4383) with an average of 5:35 of sunlight per day.