Of course it’s just the beginning of summer, but it’s the midpoint of the solar cycle. Per Wikipedia:
The solstice itself has remained a special moment of the annual cycle of the year since Neolithic times. The concentration of the observance is not on the day as we reckon it, commencing at midnight or at dawn, as it is customary for cultures following lunar calendars to place the beginning of the day on the previous eve at dusk at the moment when the Sun has set…
In the 7th century, Saint Eligius (died 659/60) warned the recently converted inhabitants of Flanders against the age-old pagan solstice celebrations. According to the Vita by his companion Ouen, he’d say: “No Christian on the feast of Saint John or the solemnity of any other saint performs solestitia [summer solstice rites] or dancing or leaping or diabolical chants.”
As Christianity entered pagan areas, midsummer celebrations came to be often borrowed and transferred into new Christian holidays, often resulting in celebrations that mixed Christian traditions with traditions derived from pagan Midsummer festivities. The 13th-century monk of Winchcomb, Gloucestershire, who compiled a book of sermons for the feast days, recorded how St. John’s Eve was celebrated in his time:
Let us speak of the revels which are accustomed to be made on St. John’s Eve, of which there are three kinds. On St. John’s Eve in certain regions the boys collect bones and certain other rubbish, and burn them, and therefrom a smoke is produced on the air. They also make brands and go about the fields with the brands. Thirdly, the wheel which they roll.
The fires, explained the monk of Winchcombe, were to drive away dragons, which were abroad on St. John’s Eve, poisoning springs and wells. The wheel that was rolled downhill he gave its explicitly solstitial explanation: The wheel is rolled to signify that the sun then rises to the highest point of its circle and at once turns back; thence it comes that the wheel is rolled.
On St John’s Day 1333 Petrarch watched women at Cologne rinsing their hands and arms in the Rhine “so that the threatening calamities of the coming year might be washed away by bathing in the river.”
So: bone-fires, leaping, chanting and mass bathing to drive away the dragons of calamity. There’s certainly enough calamities threatening this year — and we should’ve started the rites last night!
(P.S. for our readers in the Southern Hemisphere: Happy Winter Solstice!)