Airport spokeswoman Laura Coale reported no damage. Nine flights were diverted elsewhere during a tornado warning that lasted about 40 minutes, she said.
A 97 mph wind gust was measured at the airport before communication with instruments there was briefly knocked out, said National Weather Service meteorologist Kyle Fredin.
Chris Polk, a construction foreman, was working on a renovation project just outside the airport's main concourse when he got the tornado warning at 2:15 p.m., looked up and saw a funnel cloud. He and his crew ran inside and took shelter with some 100 people, including luggage-toting passengers, inside a basement break room as tornado sirens sounded.
"It got pretty crazy around here," Polk said.
Asked whether he was nervous when he spotted the funnel cloud, he shrugged. "No, I'm from Missouri," he said.
Everyone inside the break room was calm, Polk added.
It wasn't clear how many people were at the airport when a public announcement went out about the tornado warning, but the airport averages about 145,000 passengers over the course of a day, Coale said.
Television coverage showed the airport's normally busy terminal was empty during the warning. Access to a bridge to concourse A was blocked, since the bridge is surrounded by large glass windows.
Scott Morlan said he had dropped his daughter off at airport and was heading out when he saw an ominous cloud.
"It was just turning. You knew it was thinking about coming down," he said.
He watched the tip of funnel cloud touch the ground and cross Pena Boulevard, which leads to the airport, before lifting into the sky.
On Monday, a tornado touched down briefly in La Junta on Colorado's southeastern plains. Power poles were knocked down in an industrial park, but no injuries were reported, said weather service spokeswoman Nezette Rydell said.
Heavy rain fell there, as well as in Lamar, where some streets flooded. The area is among those hardest hit by the drought in the West.
La Junta Fire Chief Aaron Eveatt said high winds downed power poles, temporarily closing U.S. 50. A gas station canopy was toppled and a co-op storage tower also suffered damage.
Mark Sarlo, the manager of the Phillips 66 station, said he was driving to the station just before 6 p.m. Monday when the sky turned dark brown and yellow, the rain began to pound, and wind shook his truck. He stopped and got on the floor as debris hit.
As soon as the storm passed, Sarlo said residents in the town of 7,000 were out with chain saws removing downed poles and trees blocking streets. They also cut up his canopy and hauled it in chunks to an empty lot so he could resume business. One family brought bottled water and pizzas to feed the crews.
"It's just amazing," he said of the response of his hometown.
Associated Press writers Steven K. Paulson and Colleen Slevin contributed to this report.