I tried to figure out the jet stream. This was because it has a lot to do with weather.
Not to get complicated, but the polar jet stream dips lower in cold weather and goes up higher during warm weather. The cool air from the Arctic stays up there during the summer and comes down during the winter.

I’ll start with a diagram of the Earth’s atmosphere from NOAA.

From NASA, a picture of the jet stream from space.

This NOAA diagram shows the jet stream The sub polar is also shown.

Another diagram from NASA, this one is the winds that circle the Earth.

This means that in summer, when the jet stream is high, it is hot.

And the last picture is when the jet stream dips and it is cold.