All solid wood floors will react to the presence of moisture. In the winter heating months, moisture leaves the wood causing the floor to contract which leaves unsightly gaps between each plank. In the summer months when the humidity is higher the wood will expand and the gaps will disappear. If there is too much moisture it may cause the wood planks to cup, or buckle. This is why it is important when installing a solid strip floor to leave the proper expansion area around the perimeter and to acclimatize the wood prior to installation.