Yes, Mexicos Green Grey Porphyry can be used for exterior applications in humid climates. Porphyry is known for its durability and resistance to weathering, making it suitable for outdoor use. Its natural composition and texture also provide good slip resistance, which is important in humid areas where surfaces can become slippery due to moisture. However, it is always recommended to consult with a local expert or contractor to ensure proper installation methods and maintenance practices for specific climate conditions.