Cloud coverage usually doesn’t influence flight by itself if not connected to wind strength or approaching storms. If you observe an approaching weather system with storm conditions the weather situation could change within minutes and safe flight conditions cannot be met anymore. It is of utmost importance to land immediately if any potential signs of an approaching storm system are observed.
If it starts to rain heavily during the flight you should immediately return to the home position and land as soon as possible. Water intrusion in the pitot system is a potential hazard and sensor failure with loss of control can occur.
