What causes winds to deviate from straight-line paths?

Winds don't blow in a straight line because of the Coriolis effect. Coriolis effect is the deflectiion of all moving particales of matter at Earth's surface to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This provides evidence for the Earth's rotation. Since the wind is not attach to the Earth, it doestn't move along with the Earth. As a result, the wind curves when it blows from a high to low pressure.