WASHINGTON (AP) — The calendar said December but the warm moist air screamed of springtime. Add an eastbound storm front guided by a La Nina weather pattern into that mismatch and it spawned tornadoes that killed dozens over five U.S. states.

Tornadoes in December are unusual, but not unheard of. But the ferocity and path length of Friday night's tornadoes likely put them in a category of their own, meteorologists say. One of the twisters — if it is confirmed to have been just one — likely broke a nearly 100-year-old record for how long a tornado stayed on the ground in a path of destruction, experts said.

"One word: remarkable; unbelievable would be another," said Northern Illinois University meteorology professor Victor Gensini. "It was really a late spring type of setup in in the middle of December."

Warm weather was a crucial ingredient in this tornado outbreak, but whether climate change is a factor is not quite as clear, meteorologists say.

Scientists say figuring out how climate change is affecting the frequency of tornadoes is complicated and their understanding is still evolving. But they do say the atmospheric conditions that give rise to such outbreaks are intensifying in the winter as the planet warms. And tornado alley is shifting farther east away from the Kansas-Oklahoma area and into states where Friday's killers hit.

Here's a look at what's known about Friday's tornado outbreak and the role of climate change in such weather events.

___

Here's a look at some of the relief being provided and ways to donate

The American Red Cross is making it easy to send a quick $10 donation simply by texting “REDCROSS" addressed to the number, 90999. Other donations can be made by calling 800-733-2767 or visiting redcross.org online. Other information, including suggestions on how to find someone affected by the storm, can be found here.

The Salvation Army has set up a disaster relief fund for the tornado victims. Donations can made here or by calling 800-725-2769. It is also preparing to dispatch mobile kitchens that can serve 500 to 1,500 meals per day to the survivors and first responders in the affected areas.

World Vision, a Christian humanitarian group, plans to begin shipping relief supplies to churches in Kentucky beginning Sunday. Besides food and emergency kits, the supplies will include heaters, blankets, solar lights and mini-refrigerators. Donations to help support those efforts can be made here.

Samaritan’s Purse, another humanitarian group, said it sent disaster response teams on Saturday to Mayfield, Kentucky, and Monette, Arkansas, while other teams started to head to the devastation in Tennessee and Illinois. A tractor-trailer stocked with tools and equipment departed from Texas, according to the group, with more help on the way from North Carolina when weather allows. Donations can be made here.

Kentucky Gov. Andy Beshear announced the creation of a tornado relief fund for the western part of the state and also called on people to donate blood, which has been running in short supply during the pandemic.