When are upper air winds fastest?

The upper air winds are the fastest in the wintertime when the core wind speeds of the polar front can reach speeds of approximately 250 miles per hour. The polar jet stream travels around the earth at a height of about 5 to 8 miles above the surface.

The polar jet stream occurs when the colder air in the winter meets warmer air near the tropopause. This jet stream is one of the main conditions responsible for the weather patterns across the United States. A change in the jet stream typically leads to a change in the movement of the weather.