A severe winter storm sweeping across the central and eastern U.S. in late January 2026 is threatening states from Texas to New England with crippling freezing rain, sleet and snow. Several governors issued states of emergency as forecasters warned of hazardous travel conditions, dangerous wind chills and power outages amid bitter cold expected to linger for days.The sudden blast may come as a shock to many Americans after a mostly mild start to winter, but that warmth may be partly contributing to the ferocity of this storm.As atmospheric and climate scientists, we conduct research that aims to improve understanding of extreme weather, including what makes it more or less likely to occur and how climate change might or might not play a role.AdvertisementAdvertisementAdvertisementAdvertisementTo understand what Americans are experiencing with this winter blast, we need to look more than 20 miles above the surface of Earth, to the stratospheric polar vortex.A forecast for Jan. 26, 2026, shows the freezing line in white reaching far into Texas. The light band with arrows indicates the jet stream, and the dark band indicates the stratospheric polar vortex. The jet stream is shown at about 3.5 miles above the surface, a typical height for tracking storm systems. The polar vortex is approximately 20 miles above the surface. Mathew Barlow, CC BYWhat creates a severe winter storm like this?Multiple weather factors have to come together to produce such a large and severe storm.Winter storms typically develop where there are sharp temperature contrasts near the surface and a southward dip in the jet stream, the narrow band of fast-moving air that steers weather systems. If there is a substantial source of moisture, the storms can produce heavy rain or snow.In late January, a strong Arctic air mass from the north was creating the temperature contrast with warmer air from the south. Multiple disturbances within the jet stream were acting together to create favorable conditions for precipitation, and the storm system was able to pull moisture from the very warm Gulf of Mexico.The National Weather Service issued severe storm warnings (pink) on Jan. 24, 2026, for a large swath of the U.S. that could see sleet and heavy snow over the following days, along with ice storm warnings (dark purple) in several states and extreme cold warnings (dark blue). National Weather ServiceWhere does the polar vortex come in?The fastest winds of the jet stream occur just below the top of the troposphere, which is the lowest level of the atmosphere and ends about seven miles above Earth’s surface. Weather systems are capped at the top of the troposphere, because the atmosphere above it becom …
