Extremely heavy rain fell into a small canyon above Santa Clara, which drained into what used to be a dry wash but has since been developed with homes and businesses, said Pete Wilensky, lead forecaster for the NWS in Salt Lake City.
Between Monday evening and Tuesday at 2:44 p.m., 3.41 inches of rain fell in nearby Ivins, according to the NWS website.
A retention pond swollen by the torrential rain broke through a canal dike near Sunset Boulevard and North Canyon View Drive, unleashing a flood of muddy red water. Shortly after noon, the city had evacuated 60 homes and 15 businesses threatened by water pouring toward the Santa Clara River. Water flooded at least several homes and businesses near the intersection of Santa Clara Drive and Canyon View Drive, said Chad Hays, director of parks and trails for Santa Clara.
The waters flooded at least 10 to 15 homes, though officials were still trying to assess the extent of the damage Tuesday evening.
The Red Cross of Utah provided snacks, water and dry ground for evacuees in the first floor of the Santa Clara City Building.
Most of the water from the retention pond had stopped flowing by late Tuesday afternoon, and the city allowed people to return to their homes and businesses, some to see the damage for themselves. That included Randy Snow, owner of the Domino's Pizza at 2311 Santa Clara Drive.
His employees had only a few minutes to evacuate, just enough time for them to call their customers and let them know the store couldn't deliver. Snow arrived later that day to find two inches of water and an inch of mud had flowed through the store.
Luckily, all he had was a big mess to clean up, instead of damaged or lost property, he said.
Snow hoped to reopen Wednesday, though he doubted the parking lot or roads would be cleaned up until Thursday. The city closed Santa Clara Drive, Arrowhead Trail and Vineyard Road to traffic Tuesday, allowing only emergency vehicles and people trying to get home to pass through.
City manager Ed Dickie did not expect much more flooding late Tuesday, though the city did set up sandbags to divert water around property in case more rain comes.
The NWS was forecasting a 70 percent chance of more showers and thunderstorms before midnight Tuesday. Though there is still a chance of rain through midday Wednesday, whatever precipitation does come is unlikely to amount to "excessive amounts of water" that would cause a second deluge, Wilensky said.
Besides Santa Clara, the hardest-hit areas included the North Fork of the Virgin River, the Narrows area of Zion National Park, and the Beaver Dam Wash.
Wednesday's forecast in southwestern Utah calls for partly cloudy skies and a 30 percent chance of showers and a high of 89. Skies should clear by Thursday, as temperatures rise into the lower 90s.
Salt Lake City will see sunny skies and a high of 77 degrees on Wednesday, with temperatures warming to the mid-80s by the weekend.
Tribune reporters Cimaron Neugebauer and Bob Mims contributed to this story.