Extreme weather conditions, including flooding, snow, heat waves, and tornadoes, have affected large parts of the United States, with the jet stream stuck in a sinuous pattern that has created instability and unpredictability. The Deep South has experienced record-breaking temperatures, while California has seen cold and wet weather. The jet stream, which shapes weather patterns, has been affected by climate change, according to Jennifer Francis, senior scientist at the Woods Hole Research Center. Attribution science, which links extreme weather events to climate change, is a young field, but research has shown that global climate change has contributed to events such as Hurricane Harvey.