It is very difficult to prepare a perfectly level ice surface. Even though most imperfections can't be seen, the way the rocks behave while in motion may indicate mysterious ridges and troughs. This is part of the game. The Air The air temperature in some clubs is controlled. This is comfortable for the curlers and keeps the relative humidity low so frost won't build up on the ice.
Some clubs have dehumidification systems.
This further decreases the relative humidity.