Here in the northern mid-latitudes (much of Canada and the US, Europe, and the northern half of Asia) our weather is governed by the jet stream. This high-altitude wind current, flowing rapidly from west to east, separates cold Arctic air (to the north) from warmer temperate air (to the south). So on a given day, if you're north of the jet stream, the weather will probably be cold; if you're to the south, it will probably be warm; and if the jet stream is passing over you, you're likely to get rain or snow.
![Eigerøy lighthouse III [Explored #4]](http://static.flickr.com/2879/8805431526_732f27a085_t.jpg "Eigerøy lighthouse III [Explored #4]")
