If you are in the Central Time Zone or farther west, the summer solstice is today. But if you are in the Eastern Time Zone, it’s technically tomorrow because the solstice occurs this year at 12:24 am EDT on June 21 which is the same as 11:24 pm CDT on June 20. Those time zones!
EarthSky provides a look at the June 2017 solstice in some recent posts. The summer solstice marks the beginning of astronomical summer, although meteorological summer began on June 1. You can read about it here. They also provide more links to additional information here.