Most of us feel sleepy on the rainy day. Different people have different views about this aspect. This sleepiness may be because of the production of serotonin in our body in the dark rainy days are low. Serotonin is regulated by sunlight which effects mood.
Also the production of melatonin is increased in the dark i.e. in the rainy day. It is produced by a gland in the brain known as pineal gland. Scientists say that its formation is less in the sunlight and hence we didnâ€™t feel much sleepy on a clear day as compared to the rainy day.
One reason for this could be that moisture gives relaxation to our body like we feel much relaxed after the shower Also the rhythm raindrops falling on the earth. The pleasant climate decrease in our daily activities. Increase of quietness and stillness and the mental caress that we get from rain lead us to feel sleepy on the cool rainy day.