The jet stream is a huge current of air that moves around our planet at a very high altitude. Think of it as a steering current that moves things like weather systems, snow, and other “parts” of our weather from place to place…it is kinda like a flooding river, with currents, and all that, except that it is moving air not water. The location of the jet stream is important because, for example, in the United States, if the jet stream is farther north, the “midwest states” tend to be warmer. But, if the jet stream drops farther south, and runs across, say, Tennessee and Arkansas, that allows the cold weather from Canada in the wintertime to move farther south and it brings in colder weather.

So, in the wintertime if you will notice where the jet stream is relative to your state, you can know if the weather is going to be warmer or colder. I hope this helps.