Seasons are a gameplay mechanic in the Total War series.
Rome: Total WarEdit
In Rome: Total War, each turn is half a year, and each turn switches off between winter and summer seasons.
Medieval II: Total WarEdit
In Medieval II: Total War, each turn is two years (even though characters age at half a year per turn), and each turn switches off between winter and summer seasons.
Empire: Total WarEdit
In Empire: Total War, each turn is half a year, and each turn switches off between winter and summer seasons. Seasons can affect battlefield conditions: winter makes many regions snowing, increasing the rate at which most units tire out during battle (and giving cold-resistant units a stamina advantage).
Napoleon: Total WarEdit
In Napoleon: Total War, each turn is two weeks, so seasonal effects linger much longer: each season lasts a total of eight weeks. The way seasons impact gameplay varies depending on the campaign. In the Egypt Campaign, for example, seasons have no impact at all. For other campaigns, however, winter causes some regions to become snowy, giving units a stamina penalty.
Napoleon: Total War introduces Attrition to the Total War series, where units slowly lose men after each turn of facing extreme heat or cold. In the winter season, cold attrition takes its toll on many regions in most campaigns. There is functionally little to no difference among the summer, spring, or autumn seasons however.
Total War: Shogun 2Edit
In Total War: Shogun 2, Seasons affect the economy, with the Spring and Summer months providing a boost to income while winter causes the reverse to happen.
Fall of the SamuraiEdit
Total War: Three KingdomsEdit
For more information, see Seasons (Total War: Three Kingdoms).