Wind direction is primarily determined by differences in air pressure, with air moving from areas of high pressure to areas of low pressure. The rotation of the Earth does play a role in wind direction, but its effect is relatively small.

The Coriolis effect is a force that deflects moving objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection is caused by the Earth's rotation, and it is what gives winds their characteristic curvature. However, the Coriolis effect is only significant for large-scale wind systems, such as hurricanes and jet streams. For smaller-scale winds, such as those that occur near the ground, the Coriolis effect is negligible.

The main factors that determine wind direction are the pressure gradient force, which is the force that drives air from areas of high pressure to areas of low pressure, and the frictional force, which is the force that opposes air motion. The Coriolis effect is a secondary factor that can influence wind direction, but its effect is generally small.