You don’t want to wear your leather band every day anyway; it’ll degrade faster if you don’t give it time to rest.
Here are the general leather care instructions Hermès provides:
https://www.hermes.com/us/en/story/89726-leathercareinstructions/
You can still wear it during the summer; avoid particularly humid days and sunlight but dress up with it during cooler evenings, etc.. You’re strongly encouraged to swap with the sport band when getting wet/sweaty, and having multiple leather bands to swap around as to not wear any one down quicker is a good idea. Wearing the same leather band every day will degrade it faster as the creases and bends will be constantly stressed with little chance to relax.
The Jumping bands are a good option to swap in, still premium but breathable.