For caravanning in the UK I usually plan my tours during the winter then check that I've got a clear two weeks in the diary then look at the 10-day weather forecast. If all is good I start booking, usually at CC sites. By then of course all the weekends are fully booked so I have to resort to CLs. I'm just back from a couple of weeks in Yorkshire and North Wales which was brilliant. I've written it up in my blog:
https://jondogoescaravanning.wordpress.com/a-tour-of-the-yorkshire-dales-north-wales-june-2015/