How the Jet Stream Influenced Two Major Weather Situations in 2025

The summer and fall of 2025 will forever be remembered for two distinct weather extremes. On one end of the spectrum was a summer that saw unprecedented flash flooding. On the opposite end of the extremes was a tropical weather season that saw no hurricane landfalls in the mainland U.S. Meteorologists say that the jet stream was a major player in both of these scenarios. How did the polar jet stream influence these situations? Read on for the details.

Understanding the Function of the Jet Stream

Jet streams are defined as narrow bands of powerful winds that circulate in the upper troposphere approximately 4 to 8 miles above the surface of the Earth. These winds flow from west to east across the globe, forming in areas with sharp gradients in temperatures.

The specific polar jet stream typically moves near 50 to 60 degrees latitude, putting it across Canada in the Northern Hemisphere. This is the part of the planet where the Arctic air to the north naturally clashes with the warmer air at the midlatitudes. The polar jet stream is a significant driver of the weather at these latitudes. For example, this jet stream is usually the element that sends the cold winter storms down from Canada and into the U.S.