If it’s not a matter of signal strength could it be that the weather is impacting the structure of the cable? It would seem if that were the case the signal would be “all or nothing”.
Well, it is in a loose sense all or nothing. But I'll bet you the direct-tv receiver is outputting 1080i, while BD sources are 1080p. Big difference in signal bandwidth, makes sense that one starts to fail while the other does not.
Interesting problem, I have not seen this come up with HDMI. Most concerns with data cabling in difficult environments that I'm familiar with have almost everything to do with connectorization issues, exposure to chemicals, UV, high flex requirements, etc.
REally high temperatures can obviously compromise the insulation of the cable, and very cold environments make the cable brittle and very prone to breakage, including of the inner conductor.
My guess, though only vaguely so, is that the cold/hot change has either affected the pair spacing, impacting bandwidth, or with cold/hot cycling and stress on the conductors that there may be tiny cracks in a conductor or something. I'm not really aware of HDMI cables specifically designed for these kinds of environments. I do know that category cables exist with designs for very difficult environments, you might want to talk to Kurt at Blue-Jeans about the capabilities of their cabling, from Belden, because I know that Belden sells a variety of industrial data-cabling products. Might be worth a try. Though this is a new problem that's for sure! I would look at replacing the cable though, and see what happens in the future with weather changes.