1. Leather hats should be periodically treated with leather dressing like minks oil, neatsfoot oil, Lexol/Brik4 or similar products. Be sure to avoid saddle soap, as that may dry your leather hat. (Oiled leather hats tend to require less attention.)
2. Once conditioned, your hat is ready to wear in any season. Avoid getting your hat wet, then placing it near heat. Also, avoid placing your hat in direct sunlight for extended periods, as such exposure may shrink the hat to a smaller size.