Straight-line winds are caused by a difference in air temperature and density within a thunderstorm. When cool, dry air forms inside a thunderstorm, condensation and rain can continue to cool it until it eventually becomes heavier than the surrounding warmer air. This weight difference, paired with the shift in temperature and density, results in a sudden downburst of air. When the cool air reaches the surface of the Earth, it spreads outward, resulting in strong winds that can damage homes, vehicles, trees, and other structures.
Given the severity of the damage that can be caused by straight-line winds, if a straight-line wind warning is issued in your area, seek shelter as if it were a tornado. Basements, closets, and other interior rooms away from windows are some of the best locations in which to take shelter during straight-line winds. If you are unable to make it to any of these locations, getting under heavy furniture, such as a dining table, can help to protect you from broken glass or other falling objects.