Start of Summer?

Summer: A period of fruition, fulfillment, happiness or beauty. 

When does summer start? Its a question that children always ask (at least I did as a child). Memorial Day weekend?  Meteorological  summer, June 1st? When school is finished for the year?
 Here in Ogunquit, summer season starts this weekend: warm days in the 70's & 80's. Visiting Canadians celebrating Victoria Day weekend,  most businesses are open, and the Ogunquit Musem of Art opens for the season! Memorial Day may be next week, but the town is busy with beach goers, sightseers, and chirping birds....

I went down to the beach for a bit this afternoon. There was not a cloud in the sky. I think this definition from Dictionary.com sums up summer:

The period of finest development, perfection, or beauty previous to any decline: the summer of life.