I have tested almost all variations game graphics setups When clouds are in use And only mean clouds not rain.for example light clods overcast or rain, Same result Isi silverstone isi indycar 70 fps clear sky 140 fps 20 opponents.Graphics adjustments do not affect the fps ratio between clear or cloudy sky. i5 4960 4.3 ghz asus strix gtx 1080 24 giga ddr3 ram