On Tuesday, 12 August 2014 11:06:00 UTC+1, John Hall wrote:

The weather often seems to take an autumnal
turn around mid-August (though summer sometimes returns for the first
half of September). I think it's more than just the days noticeably
getting shorter making it seem like that.

Probably a neutral point related to the solar declination. IIRC we are some 60 degrees to the sun in August. Can't remember what happens after but we often have a penchant for thundery weather around now.

Wish I could remember how often that occurs. + Got to have a lunar coincident with it.

Early in September it is some 45 degrees from us. I believe that's an important angle for some reason.
http://www.wsanford.com/~wsanford/ex...s/DEC_Sun.html
Works every year but this one is only good for 2:
http://www.moontracks.com/moon-declinations.html

If you have records of thunderstorms, look for angles or resultants divisible by 15. It used to work when I was doing that sort of thing -a bit hit and miss but my maths is crap.