There is a rain flag (white with a red cross) to be shown when there is standing water on the track. Lack of adhesion should not be used for water, but for any other issues, such as oil, melting tarmac, any fluids from a bike. IIRC the rain flag only recently came back, and they are not at all locations, so sometimes Lack of Adhesion has been shown for exceptional water conditions, such as standing water on a white line on a fast corner. Hope this helps.