The 2010 Summer Solstice in the Northern Hemisphere is Monday, June 21st at 4:28AM Yelm time.
Source: U.S. Naval Observatory

“As of Friday, Seattle still was waiting for its first daytime high this year of 75 degrees. The latest day of the year for the thermometer to reach 75 previously was June 9, 1991…

May 20, May 25 and June 3 all registered record rainfall in Olympia for those days of the year, according to Weather Service records,” quoting John Dodge in the Tacoma News Tribune.

“In case you want to remember the good ol’ days: just a year ago, we [Seattle] tied a record for the driest spring recorded,” quoting KING-5 TV.

UPDATE: JUNE 23
“Seattle inches past 75 degrees after 272-day chill”
From the Seattle P-I.