Why is leaving a house unoccupied in summer bad for timber floors?

In closed unoccupied dwellings with higher internal temperatures, timber moisture content can drop to 4%, causing a high degree of shrinkage, cupping, and at times checking (surface splits). Occupied homes have higher internal humidity from cooking, plants, showers, and evaporative coolers which helps maintain moisture levels. Floor Sanding Australia recommends maintaining some ventilation and humidity in unoccupied homes during hot seasons.