At least five people have died as a powerful storm system swept across parts of the central United States amid unseasonably warm temperatures, spawning hurricane-force winds and possible tornadoes.
In southeastern Minnesota, a local sheriff said a 65-year-old man was killed on Wednesday night when a 40-foot tree blew onto him outside his home.
In southwestern Kansas, blinding dust kicked up by the storms led to two separate crashes that killed three people. And in Iowa, a semitrailer was struck by high winds and rolled onto its side in the eastern part of the state on Wednesday evening, killing the driver, police said.
The storm shifted north of the Great Lakes into Canada on Thursday, with high winds, snow and hazardous conditions continuing in the upper Great Lakes region, the US National Weather Service said.
More than 400,000 homes and businesses were without electricity in Michigan, Wisconsin, Iowa and Kansas, according to poweroutage.us, which tracks utility reports.
The destructive weather system developed amid unprecedented warmth for December in parts of the central and northern US.
That included temperatures that rose to 21 degrees Celsius (70 degrees Fahrenheit) across southwestern Wisconsin on Wednesday evening. The Weather Company historian Chris Burt compared the heat to that of a “warm July evening”.
“I can say with some confidence that this event (the heat and tornadoes) is among the most (if not THE most) anomalous weather event ever on record for the Upper Midwest,” Burt wrote in a Facebook post.
The wild weather in the Midwest came on the heels of devastating tornadoes last weekend that cut a path through states including Arkansas, Missouri, Tennessee, Illinois and Kentucky. At least 75 people were killed in Kentucky alone, while 14 others were killed in other states.
US President Joe Biden toured Kentucky on Wednesday, pledging to do “whatever it takes” to help local authorities and residents in the aftermath of the deadly storms.
There were more than 20 new tornado reports on Wednesday, scattered mostly through eastern Nebraska and Iowa, based on preliminary reports to the Storm Prediction Center. The day also saw the most reports of hurricane-force wind gusts of any day since 2004, the centre said.
“To have this number of damaging wind storms at one time would be unusual anytime of year,” said Brian Barjenbruch, a meteorologist with the US National Weather Service in Nebraska. “But to have this happen in December is really abnormal.”
The governors of Kansas and Iowa declared states of emergency.
The winds also whipped up dust that reduced visibility to zero in parts of Kansas and caused at least four semitrailers to blow over.
Kansas deployed helicopters and other firefighting equipment to help smother at least a dozen wind-fueled wildfires in western and central counties, officials said on Thursday.
Scientists say extreme weather events and warmer temperatures are more likely to occur with human-caused climate change.
However, scientifically attributing a storm system to global warming requires specific analysis and computer simulations that take time, have not been done and sometimes show no clear connection.
“I think we also need to stop asking the question of whether or not this event was caused by climate change,” said Northern Illinois University meteorology professor Victor Gensini.
“We need to be asking, ‘To what extent did climate change play a role and how likely was this event to occur in the absence of climate change?'”
The unusually warm temperatures on Wednesday were due in part to record high ocean temperatures in the Gulf of Mexico, which would not have happened without global warming, said Jeff Masters, a Yale Climate Connections meteorologist.