My office at work has no windows so I never know if it's sunny, raining, dark, light, whatever. Its lame. It's been really hot outside BUT apparently is it today that marks the official start of summer.
It is the beginning of the summer solstice. It basically has to deal with the tilt in the Earth's axis, it causes the sun to be in the highest position (in the Northern Hemisphere anyway). No one cares about that stuff, they have festivals symbolizing its sign of "fertility."
People also wear flower bouquets in their hair too. That's totes amaze.
Next year I'm having a midsummer get together. That would be super awesome.