The transit of Venus is among the most rare of planetary alignments. Venus passes in front of the sun twice every century. Transits appear in close "pairs," so although you might have seen this special occurrence in 2004, it will not be visible again until December 2117.
On Tuesday, June 5, in most of California, you can watch the planet Venus slowly pass in front of the sun from 3:04 p.m. to 9:46 p.m. PDT.
Update 4:18 p.m. KQED QUEST is Storifying the event...
— Paco Ragageles (@pacoragageles) June 5, 2012