First, in case anyone wondered if I was being late, my Celtic League calendar says today is Midsummer Eve instead of the solstice being midsummer. Considering tomorrow is St. John's Day and there's a good bit of evidence that the British Isles Celts of at least the post-Christianization era considered that day to be midsummer, I don't see a problem with doing it myself. If there's one area where I feel a certain common ground with Celtic traditionalists despite the divides between them and reconstructionists, it's where we both believe more recent cultural patterns are just as valid a source as the older material when it comes to customs and practices. I'm attempting to build a more Celtic practice in the here and now, after all.
According to some archaeologists, the Stonehenge site wasn't used for summer solstice rituals. Rather, it was a popular spot for winter solstice rites. This is based in no small part on the remains of pig's teeth found on the site, which indicate the animals were killed while not quite a year old. That sort of pig is born in spring, so the teeth would be much smaller if they had been Midsummer sacrifices.
I am pretty sure I know how the druids of Britain will react to this data. They'll go merrily forward as they are now. Not that I blame them too much. They'd have to invest in waterproof robes to use the site in December. But if anyone thinks the concept of an outdoor festival in England in any December seems odd, they may wish to consider the evidence that England's weather changed over the centuries. After all, they used to grow wine there. That requires a more Mediterranean climate. Living in one as I do, I can assure you that a sunny December day can be pleasant enough to be outside in so long as you're wearing the right clothing. The Neolithic equivalent of a light jacket and/or sweater would be adequate, especially with a huge bonfire to keep you warm.