Timber should be well prepared when purchased and installed for flooring. This includes proper drying, so that the individual planks are straight. But homes are exposed to moisture over time, and because of this wooden flooring can suffer at least some warping.
Ideally humidity should be between 35% and 55%. Above this level the wooden floorboards can absorb some moisture, leading to warping. Below this level the floorboards can dry out, which can lead to cracking and splintering. Engineered floors are less prone to this problem than hardwood, but not wood incompletely immune to humidity and moisture issues.
Hardware stores usually sell a hygrometer that shows the moisture content of the air. These are only a rough measure, but are more than adequate for the average home. If the humidity is too high or low the levels can be adjusted. (N.B.: Do not confuse a hygrometer with a hydrometer, which measures the density of liquids.)
Some houses are fitted with a humidistat, a device that automatically adjusts the humidity on the indoor environment. Other householders can manually adjust the humidity.
Raise the moisture levels by growing and watering some leafy indoor plants. Else, use a vaporiser or humidifier to put moisture in the air. Be careful not to overdo it.
Most air conditioners will reduce the moisture content; else use a dehumidifier. Cat litter in an inconspicuous place will soak up some moisture.
If you have musical instruments, specifically wooden ones like acoustic guitars, violins or a piano, the humidity level might need to be different. Instruments stored in cases are fairly safe. Other instruments might have their tuning affected by humidity, so it pays to keep moisture levels at optimum. 45% humidity tend to be safe, but check with a manufacturer to see if your instrument has specific requirements.
Maintaining the right humidity keeps the floorboards in good condition, free from warping. It also tends to be much better for the occupants health. Monitoring the humidity has a host of benefits.