Welcome to the Out Run weather mod that will let you enjoy some arcade clouds on Assetto Corsa.
Download the mod, unzip and copy to "\Assetto Corsa\content\weather\".
For this weather mod to look like above you need to use the Peter Boese clouds that you can find inside the Wagnum's Graphics Mod at http://www.racedepartment.com/downloads/wagnums-graphics-mod.8725/
You can copy the Peter Boese clouds directly to "\Assetto Corsa\content\texture\clouds", deleting first the original Kunos clouds.
Or if you use Content Manager you can copy the Peter Boese clouds to "\Assetto Corsa\content\weather\4_out_run_warm\clouds" and "\Assetto Corsa\content\weather\4_out_run_cold\clouds" and Content Manager will load them when you select any of my weathers.