Last summer we started having problems with receiving Sky channels. Somewhere around here there's a thread where I discussed this. Anyway, it came right then packed it in again at Easter. Sky ran us through all the over-the-phone tests then said they would get someone out in three weeks. This never happened. It settled down then started again two months ago. This time, none of TV1, 2, or 3 would come on. A message came up saying that "due to atmospheric conditions..." blah blah. Sky insisted it wasn't their gear since these channels would come up intermittently. So, we started having recordings that either didn't happen or that missed large chunks due to there being no signal. 

Tv1, 2 & 3 died. They just wouldn't come up at all. On the day we hit 26C. Sky claimed they couldn't get anyone out for 6 weeks. We were able to insist that we knew it was definitely a Sky fault and demanded to see a tech asap. 

It was the old dish fittings. The same ones that people here run into issues with for rain fade on hot days. Ours were two generations behind and had been failing for well over a year. 

Long story short - if you get rain fade and signal loss on hot days call Sky and get a tech out. Its a known problem with the previous two generations of dish and is quickly and easily fixed.