The Enhanced Fujita Scale is used to assign tornadoes a rating based on estimated wind speeds and damage.
The EF Scale became operational on Feb. 1, 2007. It was revised from the original Fujita Scale, developed in 1971 by Tetsuya Fujita, to better reflect wind speed with damage observed in tornado surveys.
Deadly Severe Weather Facts & Safety Tips:
Between 3 and 6 feet of snow and plunging temperatures have left thousands snowed in over upstate New York, and the cold and snow has taken lives.
A storm riding a surge of springlike warmth will bring a round of severe weather including the risk of a few tornadoes this weekend in the South as Thanksgiving travel begins.
After a pause in the lake-effect snow on Wednesday, more bands of heavy snow will continue to pummel areas downwind of the Great Lakes, including northern and western New York, Thursday into Friday.
A shift in the weather pattern in early December will deliver some relief for the 200 million people across the U.S. being blasted by bitter air.
There will travel trouble spots for Thanksgiving travel through Wednesday including areas of winterlike conditions and rain-related issues.
Following waves of arctic cold and snow, more typical of January, a few days of springlike weather are on the way for the South, Midwest and Northeast starting this weekend.
Chicago, IL (1985)
November precipitation record: 7.65 inches (old record of 6.95 inches set in 1982). Note: November 1985 ended up with a total of 8.22 inches in city of Chicago.
State College, PA (1989)
A severe thunderstorm with an unofficial wind gust of 80 mph. Four hours later, there were snow flurries and a coating of snow.
Rapid City, SD (1996)
Temperature at Rapid City was 21 degrees. At an elevation of 5,000 feet, it was 50.