There is some risk in cleaning windows at height. If you are using safety equipment such as a harness, ladder or a foothold, you should be safe. However, if there is no access equipment available, it is possible to clean windows at height without risk provided that the following conditions are met:
The window to be cleaned is high up and can be reached without having to go outside
The window can be reached safely using a ladder or a harness
You wear suitable safety equipment such as a helmet and gloves