What aspects of climate differ between regions with rain forests and regions with savanna vegetation?

[Ottawa Mike]

This question looks like it should be in the weather or geography sections.

[Soilguy]

The difference is the amount of rainfall.

Of all the vegetation types, trees require the most water. When there isn't enough water available to support trees, plants which use less water tend to dominate the area.

A savanna is an intermediate ecosystem between forest and grassland, which has widely spaced trees surrounded by grassland vegetation. If rainfall increases, the trees will increase and eventually turn the area into a forest. If it becomes dryer, it will likely turn the area into a grassland.