Happy Summer solstice!
Here's a little legend about the Summer solstice I'd like to share with you, which relates with Saint John's day and Litha with the bonfire thing.
Basically, in the canarian island of Tenerife, they say inside the big volcano called Teide a god called Guayota (evil and very angry guy) is caged and sleeps in constant hibernation. Legend says that when the Teide erupts is because he wakes up, and he intends to do that when summer comes.
The original folks from Tenerife got the idea of lighting bonfires on the Summer Solstice so when Guayota opens his eyes to see if it's summer already he sees the bonfires and thinks it's still winter.
It's not exactly the most ellaborate (also I don't remember much more detail) story ever but I think it's pretty cool.