In the native habitats of many Haworthia species, the prevailing cool onshore winds bring low cloud, fog or drizzle to the plants. In high humidity, Haworthias generally grow faster and develop fleshier leaves.
In a dry climate, enclosed space like a greenhouse helps retain moisture. However, attention needs to be paid. When exposed to direct sunlight, the air can heat up quickly if the area is not properly ventilated. A moist and hot environment promotes fungal growth which causes Haworthias to rot, especially for the ones with fresh wounds. For the same reason, it is recommended to keep the humidity low in hot weather.