In the summer when humidity as its highest the wood absorbs the moisture and expands. This
makes the wood strips push against one another causing "cupping". Using a dehumidifier will help
prevent this condition.
In the winter when the heat is on the humidity level in the house will drop, causing the wood to
contract or shrink. Small gaps will appear between the wood strips. Using a humidifier will put
moisture back into the air and help prevent any shrinkage.
Just remember, your new hardwood floor's worst enemies are water, soap, and sand. Vacuum (using your vacuum's hard surface attachment) or sweep regularly and don't use a wet mop, commercial soaps, or floor steamers, as these products can cause you to lose your warranty.
All you need is a damp cloth and the care products recommended by the manufacturer.