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Column: Denver still remembers this massive hail storm
Rudi Kiefer

My flight from San Francisco, some years ago, was crossing the eastern edge of the Rocky Mountains. Colorado’s Golden Gate Canyon State Park lay below us. Then the ground surface suddenly dropped down as the mountain ranges ended in a sharp line. The city of Denver appeared an entire mile farther below.

At City Center Park, Denver’s elevation is 5,229 feet. Beyond Golden, 12 miles to the west, the mountains rise steeply. Just 15 miles from there as the crow flies, Squaw Mountain and nearby Chief Mountain reach heights beyond 11,000 feet. 

Denver is at a geographic latitude (or distance from the equator) comparable to Baltimore, Maryland. This puts the area into the reach of cold, dry air masses from the northwest, just like Baltimore. Conversely, 39 to 40 degrees of latitude is close enough to the subtropics for warm air to visit from the south. But Denver lacks the nearby ocean water which has a moderating effect on Baltimore’s weather. In Denver, things can get quirky, given the mile-high elevation differences and the exposure to a variety of air masses. 

June 20, 2021 marks the 20th anniversary of such an event. In 2001, June 20 began as a pleasant day. By 3 p.m., the daytime high topped out at 79 degrees at Denver International Airport. A cold front that had passed through the area a couple of days earlier had become stationary over Oklahoma. As most air south of the front was fighting with drier air to the north, storm clouds advanced toward Denver. 

Shortly after 7 p.m. that day, the sky looked ominous.  Tall, dark clouds were approaching Interstate 70. The wind started to reach speeds of 45 mph. That’s within the range of a tropical storm. At Denver International Airport, people in the parking lots ran for shelter as hail began to fall. Or, rather, began shooting out of the sky. Golf ball-sized projectiles of ice were hitting cars, rooftops and everything else with great velocity. They damaged 100 airplanes and punched the characteristic hail craters into several hundred cars. Colorado State University’s CHILL radar showed the storm moving east to the town of Watkins, where the hail stones grew even bigger and punched holes into rooftops. 

When it comes to quirky weather, Colorado is already known as the “hail capital of the U.S.”. But today’s date, 20 years back, marks an event that Denver still remembers.

Rudi Kiefer, Ph.D., is a professor at Brenau University, teaching physical and health sciences on Brenau’s Georgia campuses and in China. His column appears Sundays and at