SALT LAKE CITY (ABC4) – It was nearly 1 p.m. on August 11, 1999.

Herriman had just seen golf ball-sized hail, and it was getting worse. Some say they even saw something swirling.

Then the improbable happened: a tornado began ripping through downtown Salt Lake City. It kept swirling, gathering up pieces of buildings and windows and tossing them around as it headed toward Temple Square.

It began forming near Pacific Avenue and Concord Street, as you can see in this video from meteorologist Cesar Cornejo. The tornado then moved toward the Rio Grande District and caused minor damage.

The tornado continued northeast, killing one man at Outdoor Retailers Shows and injuring four workers at the Church of Jesus Christ of Latter-day Saints’ Conference Center.

People at the Temple for a wedding had to huddle together. In the video below, you can see how the tornado affected the wedding party. The video was shared with by Darren Schmitt.

Afterward, it caused extensive damage to Memory Grove Park and severe damage to over 150 Avenue homes.

Officials later determined the tornado was a category F2, reporting winds between 113 and 157 mph. Its path stretched eight miles and was estimated to be at 200 yards wide.

Below is a slideshow of photos of the damage after the tornado ripped through the city.

Over 100 people were injured, many critically. Miraculously, just one person was killed – 38-year-old Allen Crandy, who was supervising the set-up of a booth at the Outdoor Retailers Show. This was the first time someone died in a Utah tornado since 1884.

About 300 buildings were damaged or destroyed, as were about 800 trees. It is estimated the tornado caused $170 million in damages.

What lead up to the tornado?

A unique atmospheric setup is responsible for the genesis of the rare tornado. A strong trough lagging over northeastern Utah, and a southerly flow moving higher warm air, raised the dewpoints to the mid and upper fifties, setting up a perfect situation for the tornado to form.

The weak breeze off of the lake is what meteorologists refer to as low-level wind sheer another key ingredient in forming the tornado. As the storm started swirling and spinning, it intensified rapidly, by the time it reached downtown Salt Lake City, cloud tops had reached over 40,000 feet. The destruction was fast and terrifying. The F2 twister stayed on the ground for almost 15 minutes.

Interestingly, the Salt Lake tornado’s vortex itself began from the ground up, not the sky down.

WATCH: ABC4’s Craig Wirth looks back on the 1999 Salt Lake City tornado

Compared to technology now, meteorologists had a very limited view of the storm, the brand new NEXRAD radar at the airport, and a National Weather Service image from Promontory Point. As the storm evolved directly over the city, radar could not keep up, it took several minutes at the time to make a complete revolution, there was not really any lead time to warn residents of the city or issue a tornado emergency and sound the disaster sirens.

Utah averages two tornadoes a year. Most of the time they are not as strong as the one in 1999.

What happened next?

Residents headed out to survey the damage and help others clear up the damage.

“Anyone 15 years old who wants to volunteer please show up at Memory Grove at 8 a.m. Tuesday morning,” said Mayor Dee Dee Corradini back in 1999.

And folks came to rescue their city. They worked day after day until most of the rubble was gone. Then-President Bill Clinton and the federal government declared the city a disaster area, providing funds to help with clean up.

Some days will never be forgotten. Now, 22 years later, many Utahns still remember the day a tornado tore through Salt Lake City.