Why is it that during changing weather, one is advised to avoid closed, crowded and air conditioned places like cinema halls etc?

Explanation

During changing weather one is advised to avoid crowded places, because changing seasons are the time when infectious agents are more prevalent as moist condition favoures pathogen to grow fast and people are more vulnerable as their body system is busy ub adapting the changing environmental conditions of temperature humidity, etc and they get infected to there pathogen easily.