What does a larger number of stomata indicate about the climate?

A large number of stomata indicates that the climate is tropical, having lots of rainfall as well as lots of heat.

This is because the function of stomata is to allow water vapour to escape, which forces water molecules from the root cells up through the plant. A large amount of heat would make more water molecules within the plant water vapour, which would mean that their must be a lot of rain in order to compensate for lost water. Otherwise, having lots of stomata may be more of a disadvantage to the plant