Why should we wear cotton clothes in summer season?

There are a number of reasons to prefer cotton clothing in the summer as compared to synthetic fabrics. The most important among them is the ability of cotton to absorb moisture quickly and lose it to the atmosphere readily. During summer time, we tend to perspire a lot (which is a mechanism to keep the body cool), and we need clothing that will absorb all the resultant moisture and ensure that we stay comfortable. Cotton is the right choice of fabric as it absorbs the moisture from our body quite easily. Cotton also has the ability to lose this moisture to the air, thereby keeping us comfortable.
Cotton allows better air circulation, which ensures that our body stays dry and cool and hence minimizes the chances of fungal breeding. Light-colored cotton clothing also reflects sunlight and helps us stay cool. Cotton clothing is also better for people who have sensitive skin. 
 Hope this helps.