Control the storage environment
Store a clean, fully dry bag in a breathable dust cover with light internal support. Keep it away from damp walls, direct sun, bathroom steam and strong air-conditioning vents. Do not seal leather in plastic for long periods; trapped moisture can encourage mildew.
Respond to rain carefully
Blot water gently with a clean soft cloth and let the bag dry at room temperature, supported in its natural shape. Keep it away from hair dryers, heaters and direct sunlight. Once dry, follow the maker's instructions for the particular leather; avoid applying oils or conditioners without checking compatibility.
Prevent mould and transfer
Give stored pieces airflow and inspect them periodically during the wet season. Avoid storing bags while damp or with wet umbrellas inside. Keep light-coloured leather away from dark denim and freshly dyed fabrics, and keep cosmetics, hand sanitiser and ink in a separate pouch.
Know when to call a specialist
If you see mould, tackiness, peeling finish, deep water marks or a persistent odour, isolate the item and seek a leather-care professional. Brushing mould at home or applying household cleaners can spread spores or permanently alter the finish.