It is unclear whether Chinas Lotus Slate can be used in exterior applications in very humid climates as there is limited information available about this specific product. However, traditionally, slate is considered a durable and weather-resistant material that can withstand various climate conditions, including high humidity. It is advisable to check the manufacturers specifications and recommendations for the product to ensure its suitability for exterior use in humid climates. Additionally, proper installation and maintenance practices play a crucial role in the longevity and performance of any product used in such conditions.