I have to have my clouds on 10% at all times. When I go to live weather and there happens to be any overcast layer, it drops my frame rate to below 6-8fps and the game is unplayable. I have to then override all weather to clear/clear/clear to keep the frame rate up. I have a 1 GB graphics card and I do not even use HDR. I have an intel core I-5 3330 4 core CPU @ 3Ghz, 8192 RAM, and a NVIDIA GT 640.