What type of porcelain tile can be used outside in a state with mild climate?

Porcelain Tiles are typically rated for water absorption. >.05% is very standard for a porcelain tile. There is also an industry rating system for ceramic/porcelain tile; the P.E.I. rating offers a recommendation level for usage with regards to traffic levels and application for walls/floors and/or residential/commercial use. Porcelain tiles are completely suitable for exterior use with regards to construction. However, the type of surface finishing is also a factor in suitability. A "wet" or "glossy" glazed finish would not provide good traction for footing. Again, the industry offers specifications that list the coeffient rating of slip resistance. Lastly, only a premium, modified thin set mortar with a full admix of acrylic liquid should be used for installation for a proper bond. Proper consideration should also be given to expansion joints when installed over concrete/cement and the use of a proper non-coupling /anti-fracture membrane system over an approved wood substrate. The grout should also be a premium grade sanded grout that will resist efflourence. Anodized metal tile edge should not be used where direct sunlight is as this will cause expansion and contraction of the metal and possible installation failure. Exterior installations require above 15 degree(C) temperatures for 2 weeks during installation and drying/curing time. Proper hydration of the setting materials can take 3-5 days before grouting can be completed. Installations must not experience a "flash" or "swing" in temperature or humidity during this period. Ceramic and natural stone is not suitable for exterior installations were temperatures can freeze as water absorption will lead to freezing and cracking of tile. Some Slate (Quartzite) can be used with proper sealers applied. Sealing of grout joints is recommended regardless with a premium grade grout sealer.