What would happen if there is no water vapour in the air? Would there be any climate and weather changes during the year?​

if there would be no water vapours in in air then rain is a far away thing there would be no lakes sea or ponds on earth and water cycle would be destroyed completely trees would destroy this would lead to destruction of mankind

 In order for that to happen, there would first have to be no water on earth - no oceans, seas, lakes, rivers, snow, rain. And, if this were the case there would be no clouds which are formed from the evaporation of these land waters and which moistens the air making it habitable to breath. 

With no water - life on earth (as we know it) would no longer survive. Hope this helped.

the temperature would become cool

Yes.