Without accounting safety issues on the asset being exposed to possible depredation, nor considering market viability of the enterprise, it is worthy to mention that equipment installed in harsh environments requires an industrial type specification, which is, it has an upper allowable operating temperature range if compared to commercial rated ones. As it will be exposed to other factors such as humidity, sea air, rain, etc ... you will have to seriously consider using at least an IP-65 enclosure. As for cooling itself, in my opinion, you should either use high-flow forced ventilation, or this in conjunction with Peltier-based refrigeration, but an external cover (a 'roof') greatly attenuates the heat radiated from the case walls due to Sun radiation.