When evaluating the need for humidification, it is important to know what happens to the air around us. As reference material we can use European Normal Year, which describes the climate in our part of Europe. The diagram covers the humidity need over a period of one year.

This actually shows that there is a need for humidifying on almost all days in the year; but of course the need varies from one day to the other.

If the room temperature is rising, more humidity is required to maintain the relative humidity.
A temperature rise of just 2°C requires 10% more water. The increased running factor will also occur, if the air exchange is increased during the summer periods i.e. to cool in the production room.