Al Roker says the polar vortex is real and not a "liberal media conspiracy" like conservative radio show host Rush Limbaugh claims.
And pulled out a 1959 American Meteorological Society glossary on Wednesday's "Today" show to prove it.
"Let me tell you something," Roker said on "Today," while pointing to a photo of the term defined in his old college textbook.
"We've never used the phrase 'global warming' or 'climate change' in conjunction with this... Okay?! So for all the doubters out there, stuff it."
Roker also tweeted a photo of the term from his textbook, saying it's "Meteorology 101. No political agenda."
On Monday, Limbaugh took to the airwaves call the polar vortex, which has been blamed for the bitter cold gripping the country, a "hoax."
"We are having a record-breaking cold snap in many parts of the country," Limbaugh said on his radio show.
"And right on schedule the media have to come up with a way to make it sound like it's completely unprecedented. Because they've got to find a way to attach this to the global warming agenda, and they have. It's called the 'polar vortex.' The dreaded polar vortex."
"The hoax continues," he added.