These maps show winter temperature patterns (top) and winter precipitation patterns (bottom) associated with a curvy jet stream (not shown) that moves north from the Pacific to the Yukon and Alaska, then plunges down over the Canadian plains and into the eastern United States. A University of Utah-led study shows that starting 4,000 years ago, the jet stream tended to become curvier than it was between 8,000 and 4,000 years ago, and suggests global warming will enhance such curviness and thus frigid weather in the eastern states similar to this past winter's. The curvy jet stream brought abnormally warm temperatures (red and orange) to the West and Alaska and an abnormal deep freeze (blue) to the East this past winter, similar to what is shown in the top map, except the upper Midwest was colder than shown. The bottom map of a typical curvy jet stream precipitation pattern shows how that normally brings dry winters to reddish-orange areas and wet winters to blue regions. Precipitation patterns this winter matched the bottom map in many regions, except California was drier than expected and the upper Midwest was wetter than expected.