Source: Climate Reanalyze | The New York Times

❄️ Polar vortex

The polar vortex is a large area of low pressure and cold air that surrounds the Earth's poles. It is a natural occurrence that has existed for millions of years. The polar vortex is typically strongest during the winter months, when it helps to keep cold polar air trapped near the poles.

However, it can become disrupted and move southward. This happens when the jet stream, a strong wind that circles the Earth, changes shape and becomes wavy. The polar vortex can also split into smaller pieces that move southward. When this happens, temperatures in the Arctic can rise, and cold Arctic air can move to lower latitudes. If the movement of the cold air is strong enough, temperatures in affected areas can drop quickly and remain very low for a long time until the polar vortex returns to its normal position in the Arctic.

2021 Texas deep freeze

[Cold temperatures lead to freezing rain and a major pile up on I-35 in Fort Worth, Texas February 11th that involved 133 vehicles and multiple fatalities and injuries.] | Source

In the US, cold snaps caused by the polar vortex happen regularly. One particularly severe one occurred in Texas in February 2021, causing temperatures to drop as much as 40 degrees Fahrenheit below normal and leading to at least 250 deaths and major damage to the state's power infrastructure. As the Earth's temperature increases due to carbon dioxide emissions, the Arctic is warming faster than other parts of the world and its sea ice is shrinking. Scientists are still studying the role of climate change in the polar vortex and whether extreme cold snaps will become more common as the Earth warms.