Warm air holds more water. This can be great for leaf health, or it can lead to mold growth in tiny folds. Excessively dry air can tax or stress plants; at the wrong time of their development, this can be fatal. To keep your plants in great shape, consistent humidity is critical. To prevent fungi and mold, moving air is also critical. Your humidity monitor placement can have a big impact on keeping a consistent level of moisture in the air.