Nine states have strong gusts of wind. Dust storms in Colorado and wind-fanned fires in Kansas. There were tornadoes in Minnesota and western Iowa. The temperature in Omaha and Des Moines was a record.
100 million Americans were under some form of weather alert on Wednesday, when a powerful storm swept through the Midwest.
The combination of heat and dry has not been seen before, according to a geosciences professor at Fort Hays State University. The month of December was unusual and made you ask questions.
One key question is what role global warming might have played in fueling such an extreme weather event. It could be difficult to untangle the links between this week's storm and climate change, although it appeared to be helped by record warmth across much of the country.
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As the planet warms up, the United States can expect more unusual storms, potentially hitting in new places or at unexpected times of year. Scientists say the risks of increasingly wild weather make it all the more urgent that cities and states take steps to protect people and property.
John Allen, an associate meteorology professor at Central Michigan University, said that they expect an increase in favorable conditions for storms. We have to be aware that we can have extreme events in places that we haven't thought of before.
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In Niwot, Colo., a dust storm appeared poised to swallow the town.
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A truck was damaged by winds on a highway near Lincoln, Neb.
Warm, moist air creating updrafts and wind shear, a change in wind speed and direction can allow storms to become stronger. A hot day or a cold front can cause storms to form, which can be more unpredictable.
Studies have shown that favorable conditions for severe storms in the United States will increase as global warming progresses. The increase is expected to be more pronounced during cooler seasons that don't see as many storms, such as early spring, fall and winter, due to the presence of more warm, humid air during periods of higher wind shear.
It's not certain if those storms will lead to more tornadoes. There isn't clear evidence that tornadoes have changed in intensity over the past 40 to 60 years.
In recent years tornadoes seem to be occurring in greater clusters, and the region known as tornado alley in the Great Plains, where most tornadoes occur, appears to be shifting eastward.
There is a chance that derechos may shift into new regions or become more common as the planet warms, particularly during cooler seasons where they haven't traditionally been.
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A tornado ripped off the roof of a library in Rudd, Iowa.
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There are fires near Natoma, Kansas.
Harold Brooks is a senior research scientist at the National Severe Storms Laboratory. You might expect them to increase if you make it more summery.
While their winds are not strong enough to destroy buildings, they take out power lines and trees over a large area. There may be intense destruction in the middle of the tornado paths. In a derecho, it covers a lot more.
Professional weather watchers were shocked by the weather this week. The Iowa Storm Chasing Network head said he had never experienced such strange weather in December.
He said that it felt like spring when there were people wearing shorts, but once the storm front hit, it felt like it was snowing. It was eerie to be chasing tornadoes 10 days before Christmas. While tornado sirens were going off, we were listening to Jingle Bells in our vehicles.
The storm this week was so unusual and had so many different forces behind it that it can be difficult to disentangle the impact of global warming compared to other factors.
The storm was a mess. Is this a one-time event? Maybe it won't repeat for a long time. Will the season change a lot? I don't think we know.
Victor Gensini, a professor of meteorology at Northern Illinois University, said that all extreme weather events are now taking place against the backdrop of an atmosphere that has been shaped by humans burning fossil fuels. He said that all extreme weather events are impacted by climate change.
He said the better question is to what extent climate change might have enhanced the extreme weather event or how likely it was to occur without climate change.
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The highway between Mullinville, Kan., and Dodge City is littered with debris.
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Dust covered the sun in Jetmore, Kan.
Scientists have been able to answer those questions for numerous other extreme weather events, such as this year's deadly heat wave in the Pacific Northwest or severe flooding in Germany and Belgium, by using computer models to determine if global warming made them more likely or worse. It is not known whether any researchers try to do something similar for this week.
Discussing the role of climate change is only part of the story for some scientists. Society should do as much as possible to reduce vulnerability to extreme weather, regardless of whether or not scientists decide on an answer.
Stephen Strader, a disaster scientist at Villanova University, said that there are a lot of things we can do to protect people today.
Many states in tornado-prone areas still aren't doing enough to strengthen and enforce building codes in ways that have been proven to save lives While the accuracy of tornado warnings has improved, there is still more work that needs to be done to make them more effective so that people are aware of them.
There are always two sides to disasters. There are both climate and society vulnerabilities. We can address climate change, but we need to focus on improving survivability against extreme events.
