A Grow Tent is basically a portable greenhouse and it comes with built-in lighting and heating facilities. You have a low relative humidity which means that there is not enough water vapor to be held within your air space. Humidity is the amount of water vapor in the air. Relative humidity is the ratio of the amount of water vapor in the air compared to the total amount of water vapor present. You can find the relative humidity using the hygrometer in your grow tent. A relative humidity of 50% or more is usually ideal for plant growth. Raising the humidity level in your Grow Tent is something that you should do at least once a week, as too low humidity levels can cause some plants to wilt.