weird weather

So, I've noticed a couple of times now, I'll have the "download real-world weather" option going, and for some reason over certain areas it goes all haywire. Like the other day, it was about 60 something degrees with clear skies in real life on the U.S. east coast, and when I took off, it was that way in FSX too. But then I got to where I was going (DCA) and all of a sudden, right about when I got within 20 miles of the airport, an all-covering overcast shows up at about 2,000 feet. And then over Andrews AFB: snow. What gives?
It might not have bothered me so much if ATC hadn't assigned me a visual approach before the clouds and snow suddenly appeared (and as an aside, it's really kind of irritating how you generally can't fly the actual visual approaches into DCA to avoid prohibited airspace without ATC clearing some AI plane for landing that's flying right over the Capitol at 1,200 feet or something, thereby messing you up completely right when you need to be getting ready for a last-second turn onto the runway and all...)
Anyway, has anyone else seen this kind of weirdness with the weather, and is there anything to do about it? Or should I just get used to it?
It might not have bothered me so much if ATC hadn't assigned me a visual approach before the clouds and snow suddenly appeared (and as an aside, it's really kind of irritating how you generally can't fly the actual visual approaches into DCA to avoid prohibited airspace without ATC clearing some AI plane for landing that's flying right over the Capitol at 1,200 feet or something, thereby messing you up completely right when you need to be getting ready for a last-second turn onto the runway and all...)
Anyway, has anyone else seen this kind of weirdness with the weather, and is there anything to do about it? Or should I just get used to it?