Why so much of the US is unseasonably hot

A powerful winter storm brought deep snow to parts of the West on Monday. Much of the central U.S. was unseasonably warm: People played golf in Wisconsin and walked their dogs comfortably in Iowa, where some flower bulbs began to bloom. And high winds increased fire risk in several states.

Why did it happen?

Three things explained the strange weather in much of the US

This strong wind band traps the warm air blowing from the south beneath the cold air coming down from the north. The jet stream is constantly changing. Lately, temperatures have been far enough north to mean warm air is blowing through the normally frigid Upper Midwest.

“Its orientation is not very winter-like right now,” said Andrew Orrison, a meteorologist with the National Weather Service in College Park, Maryland.

In all weather science, it is virtually impossible to directly attribute an individual phenomenon to a specific cause. How global warming affects the position of the jet stream is a good example of this.

But climate change, caused by human activities that release plant-warming gases such as carbon dioxide, is causing global temperatures to be warmer than normal. According to the European Space Agency’s Copernicus Climate Change Service, January 2024 even broke the record for the warmest first month of the year, set earlier in 2020. January was 2.74 degrees Fahrenheit warmer than pre-industrial levels.

Also at play is a weather pattern called El Niño, which transports warm air north from the Gulf of Mexico, causing temperatures to soar in the central and eastern regions.

The East Coast will see warmer weather arrive mid-week, with cities like Washington and New York expecting temperatures well above normal.

Southern regions are also experiencing unusually warm weather, with temperatures in the 80s and 90s possible. Dallas-Fort Worth will likely be at least in the low 90s, which would break a daily record.

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