The Festival of Helios Lampontas
This is a modern innovation designed to commemorate the opposite end of the spectrum from Heliogenna which is a festival that commemorates Winter, death, and the hope of rebirth. Lampontas means "The Shining One" and during this day, we celebrate the onset of Summer, the heat of Summer, the light of the Summer Sun, etc. It is meant as a festival of laughter, of feasting, of music and sexuality all under the gaze of the all seeing.
I had thought this could be a multi day festival but in the end decided to simply make it a Holiday of one day to be commemorated on the Summer Solstice.
The Summer Solstice, of course, also reminds us that as of this day the days get shorter and Autumn and eventually Winter are not that far away, but for now, we can rejoice in the blazing heat of the summer and its many pleasures.
There is no prescription for the celebration of this day. Go to a beach, barbecue, play some loud music, make mad passionate love out doors (use common sense, of course) and above all, enjoy yourself.
Remember too those Gods that bring joy to your life. Aphrodite, goddess of laughter and beauty, Artemis, lady of the wild places, Dionysos, god of the drink, Selene, the bright moon, and even Zeus, the thunderer, who is so active in the storms of summer. (Those storms are very exhilarating)
Love, drink, and be merry.