Water vapor is the worst greenhouse gas of all.
and even that is a small percentage of the actual atmosphere- here again there would need to be a thick continuous blanket of water vapor over the world in order to bounce enough heat back to earth to cause any kind of change in daily temps- and this obviously isn’t the case, the vast majority of the atmosphere has no cloud cover at any given moment- meaning most the heat escaping the planet has nothing I n the atmosphere to prevents it’s complete escape