I also noticed faster rounds during inclement weather as fewer players out there. Colder temps, a little rain but not really hot weather. People still come out if it is really hot. At least this is based on my little keyhole of experience.
I always wondered if that's maybe why in the UK, rounds are faster - people just want to get out of the weather quicker.
Anyways, complain about slow play that I do, the cynic in me thinks it will never be a "solved" issue, so what other ways can you think to avoid it?
And thank you so much for smartphones to make a slow round more tolerable. At least you can do something interesting while waiting.