As we know , we are hot blooded animal . We don’t have capacity to adjust our body temperature according to the environmental conditions. If there is hot climatic conditions in the atmosphere we wear cotton clothes , light clothes to feel normal and fresh as during summer the temperature is more so we sweat to maintain our body temperature. Also we are advised to wear light colour clothes or white clothes as it does not absorb heat whereas black colour and dard colour absorb more heat and make us feel uncomfortable . Also for maintaining our body temperature during summers we drink cold drinks , ice tea , ice cream which provides us some relief from being hot . Uses of fan and air condition also increases .
As according to the question during winter we also need to maintain our body temperature for this we wear woollen clothes or layers to layers clothes to absorb heat and make our body hot . If we don’t wear jackets during winter we must feel so cold and even we will die due to it. So basically to maintain our natural body temperature we wear jackets. You may thinking than why animals donot wear jackets because they have fur on their body that protect them form cold conditions. In winter we also do basking in sunlight to stay normal also we shiver this process also keep us warm.
So that’s why we wear jackets during winters.