Summer doesn't begin until the Summer Solstice (longest day of the year) when the pole is at it's closest to the sun.
You do realize that the earth is actually further away from the sun in the northen hemisphere summertime? So, summer solstice is actually when the northern pole is farthest away from the sun. And secondly, summer solstice is absolutely in the middle of the summer, saying this is beginning of summer is like saying winter starts at Dec. 21st. And we all know that's wrong.
tv, iLife and iWork all announced at the same time too. The portables and desktops have not been upgraded in a reasonably long time, to wait until June would mean some models have been out for over a year, others close to. February launch would enable them to slowly bring out new models of each, finishing with WWDC.