Living in the desert southwest I’m amazed at how low the humidity can go. In the hot summer, in the single digits is not unusual.
In addition to wildfires, the lack of humidity saps the life out of musical instruments and leather. For my violin, several times a week I re-hydrate two hydration devices which go inside the case.
Leather requires help as well. Here is a dog leash that was in the pet bug out bag. I’ve ignored it for five years. Starting to crack.
I’d bought Sno-Seal for my winter hiking boots. Got beeswax in it so it should work for rejuvenating leather.
Smear it on. Let it sit. Wipe it off. That’s all there is to it. Don’t run around touching door knobs before washing your hands.