If you are an astronomer, today marks the official start of astronomical summer (for climatologists, it started on June 1). The sun reaches its northernmost point in the sky at 12:39 PM EDT. You can read about the solstice at https://www.timeanddate.com/calendar/june-solstice.html.
EarthSky also has a nice gallery of photos taken at Stonehenge in England, where the stones align according to astronomical dates (link).
Today is the longest day of the year–go out and enjoy it!
