Thanks for the question. The bokashi microbes thrive at room temperature, and out of direct sunlight. Most people choose to keep the buckets inside where the food waste is produced. If you must store the bokashi bin outdoors, then make sure that it is out of direct sunlight and does not freeze. Cold will slow microbes down so allow your bucket slightly longer to ferment in cold temperatures, and freezing can kill them given enough time.
Happy composting 🙂