Interesting. I've never heard of the sun causing an issue like that.
Wind is one of the weather features I've noticed, and part of it can be the moving trees (the same thing caused reception issues for many pelple on UHF in the analog days, and most digital signals are on UHF frequencies nowadays), but I get the impression that it's also simply the antenna moving. The rooftop antenna on my apartment complex isn't particularly obstructed by trees in the direction of the market's towers, but it certainly moves with a nice gust. That can cause pronounced problems since the wind is usually coming from the west or east, and the antenna points north, so the more it shakes, the more off-axis it's moving, and data doesn't like being tossed around like that.
Rain is another weather feature that causes problems, especially with my aforementioned CBS affiliate. If we get a light rain or drizzle, there's no problem, but a constant downpour and that thing's just gone. Oddly, thunderstorms don't affect it as badly. It'll pixelate on occasion when lightning strikes, but I've been through some fairly rough thunderstorms where that's all it does. But yes, rain is certainly an issue.
Thing is, part of your problem could also be your tuner. Not all tuners are made equal, especially digital tuners. My main setup is actually a tuner card in my living room computer. My bedroom tuner is a set-top converter. Prior to building that computer in the living room, I had two set-top boxes of the same make and model. All three of them plug into the exact same roof-top antenna. All three of them have completely different sensitivities and each one can receive some channels that the other two cannot. Additionally, with my PC-based tuner, it depends on what software I'm using to drive it, because each program attempts to decode at a different signal level. So there are a lot of factors to consider here.
heheh lol