Atmokinesis is the ability to control and manipulate the various forms and aspects of the weather itself.

This is first seen in "Control ". They have shown the capability to create and master large thunder
storms. Charlotte can also do it all by herself because she has all three powers and once levitated Emma, Rikki and Cleo all at once. 

In Battlelines, Rita was shown using this power to create a storm in a jar and was able to control wind, rain, and thunder. Nixie also demonstrated this power when she created the storm in a jar and when she made a storm cloud over Zac.