Up to 255 different climates are may be used in the one map. However, only two or three are required for pleasant transitions from, say, desert to temperate.
Climates may be 'painted' on the design map using the design map brush tool. The climate dropdown in the tool lists all the climates available to L3DT.
Climates may also be painted using the attributes map brush tool. The climate dropdown in the tool lists all the climates available to L3DT.