The December 6th issue of Jinja Shinpō had a short article about a matsuri held at a jinja in Yamagata Prefecture, Shōnai Jinja. The matsuri involves a procession, which was held this year, at reduced scale, after being cancelled last year. However, from this year the date of the matsuri has been changed from August 15th to October 6th, because of “extreme heat caused by climate change”, to quote the article.
This is the first example of such a change that I have seen, but I doubt it will be the last.
Shōnai Jinja is interesting for other reasons, as well. It was founded in 1877 to enshrine the first daimyō of the local domain, and is located on the site of the old castle. The procession is a recreation of the processions of the daimyō to Edo, to attend on the Shōgun, and was first held in 1877, on October 6th — hence the choice of the date to move it to.
There seem to be a number of jinja like this, founded in the Meiji period to enshrine daimyō — Oyama Jinja in Kanazawa is a notable example. However, they are largely ignored in historical surveys of Shinto, because they do not fit into any of the master narratives. They are not ancient prehistoric survivals, or part of Buddhist practices, or part of State Shinto veneration of the Tennō (although they were authorised by the government at that time). I am not sure how many there are, in fact. I have been to Oyama Jinja twice, and Shōnai Jinja has someone who writes lots of articles for Jinja Shinpō, so I know about them. I have come across references to others, but I haven’t seen anything systematic. If anyone is looking for a potentially very interesting PhD topic on Shinto for which documentation is likely to survive, here you go.