The app’s data showed that, in 2021, users held more than 3,600 bachelorette parties in Scottsdale, compared with around 13,000 in Nashville, said Mike Petrakis, 31, the founder and chief executive of Bach. This year, its data shows more than 11,600 parties are being planned in Scottsdale, compared with 30,000 in Nashville. If that growth rate continues in Scottsdale, Mr. Petrakis said, it has the potential to surpass Nashville in bookings. And on a recent May weekend, more than one bachelorette party attendee declared that Scottsdale is “the new Nashville.”

Robert Mayer, 35, the owner of Arizona Party Bike, said its location in Scottsdale started booking a record number of bachelorette parties in the summer of 2020. Brides were looking for a place to celebrate without pandemic restrictions, he added. Gov. Doug Ducey of Arizona, a Republican, never enacted a statewide mask mandate and reopened restaurants for indoor dining in May 2020. In Maricopa County, which includes Scottsdale, about 1,200 new Covid cases are currently being reported per day.

Mr. Mayer’s company, which is featured on Bach, leads tours of Old Town on trolley-size pedal bars, charging up to $499 (plus the cost of alcohol) for private two-hour tours for up to 15 people. His clientele is currently 75 percent women, with a median age of 28, he said. Local hot-air balloon and desert Jeep tour outfitters are also now crawling with groups of 20-something women belting out Katy Perry songs and only occasionally throwing up.

Perhaps not surprisingly, the influx has already led to disturbances. On a Saturday in May at the Arizona Party Bike depot in Old Town, Lacy Gray, 27, a company guide, had to explain the rules of the road to a bachelorette party from South Dakota after its members, sporting candy-colored wigs, took their seats at a neon pink pedal bar.

One instruction? No requests to play “‘WAP,’ specifically,” Ms. Gray said. (The song was proactively banned, Mr. Mayer added, after it drew looks from “unhappy” pedestrians.)