Fall and winter are called the vata season in Ayurveda because it is getting colder, dryer, rougher and the qualities in general are more mobile. Vata being composed of the element of space and air is extremely mobile and even volatile!
The qualities of the season are changing so we need to adapt as well to the new energy to maintain our health.
If our constitution tends to be high in vata or if we tends to have a vata dosha aggravated because of stress or travel , then the change of season will be particularly difficult. We can easily adjust our diet and lifestyle to make this transition time easier.