Why is it that during changing weather,

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

During changing weather, one is advised to avoid crowded places because changing seasons are the time- when infectious agents are more active as moist conditions favors the growth of pathogens. Also, people are more vulnerable as their body system is busy in adapting the changing environmental conditions of temperature, humidity, etc. Thus, getting easily infected by these pathogens.