If you are in a very humid place, it is best to look for the coolest hours of the day to work, as well as the coolest place. For example, if at night or early in the morning, the temperature is 5 degrees lower, that is the time to work on it.
If you have very hot hands or fondant heats up very quickly on your hands, you can wash your hands with cold water to lower the temperature. Or you can work with a damp cloth nearby, and constantly refresh them. It should be moist but not wet.
You can use air conditioning, but remember that it will speed up the drying and may not be in your best interest. Another option is to use a fan, which dries it, but not as quickly.