It doesn't. the climate affects the location of the tropical rain forests.
Almost all the tropical rainforest lies between the Tropic of Cancer (23.5° N of the equator) and the Tropic of Capricorn (23.5° S of the equator). A few pockets of rainforest lie beyond the Tropics nut never more than 28° N or S of the equator.
The rainforests themselves act as good regulators of the climates, which along with their equatorial location means that the weather is fairly consistent throughout the year and devoid of extremes. Temperatures rarely exceed 35°C or fall below 20°C even though areas surrounding the forests can be considerably warmer or cooler. Humidity is always high, typically around 80% to 90%. Rainfall is always moderate to high and can vary from about 1250mm per year to in excess of 6000mm.
A rainforest will have a very significant impact on local, national and global climate systems largely through transpiration and the exchange of atmospheric gases.
You can think of a rainforest as a giant sponge, it absorbs a great deal of the precipitation that falls upon it, a single large tree can contain several tonnes of water. With billions of trees it’s a vast amount of water that is stored up.
There’s a constant cycle whereby water is lost to the atmosphere through transpiration and absorbed from the ground via the root systems. In some rainforests, such as the Amazon, the majority of the rain that falls originated from the forest itself.
The canopy of the trees is generally very dark in colour and this enables them to absorb most of the heat energy coming from the Sun (incoming solar radiation). The lighter a surface is the more solar radiation it will reflect back into space, but the dark trees absorb about 90% of this energy.
Because the trees are absorbing so much heat it means that the air is cooler – both inside and surrounding the forest. The absorbed heat is released back into the atmosphere where it rises taking air and moisture vapour with it, this helps to accelerate precipitation and creates upward wind currents.
As the air rises above a forest it is replaced by more air that is drawn in from the surrounding areas, this can generate winds that blow toward the trees.
If there is a prevailing wind then this can carry the warm, moist air away from the forest. Because winds generally rise in the Equatorial regions and move Poleward it means that this moist air is carried either north or south (it subsequently gets deflected by the Coriolis effect and other weather systems). As the air mass cools the water vapour condenses and falls as precipitation.
In many places rainfall and weather patterns can be significantly affected by forests that are thousands of miles away. For example, precipitation in the US Midwest is influenced by forests in Central Africa and when large parts of the Indonesian forests were cut down it impacted on the weather across a region stretching from Greece and eastward to China.
Trees in general, and the rainforests in particular, are very good at extracting carbon dioxide from the atmosphere and releasing oxygen, two things that are of vital importance to life on Earth.
About 28% of the oxygen we breathe comes from the rainforests, much of the rest comes from trees outside the rainforests. Without these trees there would be a lot less oxygen on Earth.
The rainforests act as stores for huge quantities of carbon that they obtained by photosynthesising carbon dioxide from the atmosphere. If they didn’t do this then the amount of CO2 in the atmosphere would almost double and this would create a significantly warmer world.
I think it is fair to say that most, if not all, tropical forests are in the Tropics.
