Q. What are the rules concerning inclement weather?
A. The referee on site must determine if the courts are fit and safe to play. A small amount of rain can make playing on a hard court very dangerous. If there is no referee, players can rub their foot across the line. If the water on the court streaks across the line then play should probably stop. Most matches should not start in the rain. On clay courts, play may continue if a small amount of rain comes after the start of the match since it is still safe to play on a clay court with a small amount of moisture.