In traditional medicine, seasons determined what was available to us for a reason.  Our bodies needs change inherently with the environment around us.  For example, in autumn our bodies require moisture as the days cool and the browning of the foliage starts to set in.  We need foods to combat this lack of hydration. We also need to start to prepare our bodies for the ensuing winter months, reinforcing our blood which means our resilience for immune function is at a premium as well as preparing our lungs for the ensuing bacterias and onslaught of coughs, colds and flus during the winter months.