Federal Reserve Chair Jerome Powell pointed at Jackson Hole that the central bank will continue hiking rates — but that's at odds with what the data is showing, Wharton professor Jeremy Siegel said in an interview with CNBC this week. 

Out of 27 inflation indicators that have been recorded over the past month, 26 have reported below-expected figures, Siegel said. The Institute of Supply Management's Prices Index stood at 60% in July, down 18.5-points from June's 78.5%. That's the fourth largest plunge the index has recorded, and the largest slide in manufacturing since the Great Recession.

He added that the CPI typically lags behind real price plummets and that real estate prices may slide, though that will go unrecorded for some time as well. 

"The inflation news is on really on the ground, really coming in really well, and that's why I was shocked when Powell was acting last Friday like things are getting worse and worse and worse," Siegel said in an interview with CNBC on Wednesday.

At the September Federal Open Markets Committee meeting last year, half of FOMC members said there was no need to raise rates into 2022, and the most hawkish prediction was a 50-point rate hike, Siegel pointed out. The Fed has hiked the effective federal funds rate by 150 points this year so far. 

"So do they really have the ability to see the future? Not really … it was just a year ago that everyone said I'm not even thinking about thinking about raising rates," he said. 

"I don't think they need to go higher than that. And steering the market by saying, 'We're going to stay high through 2023' when they have no idea what's going to be happening in 2023. It was really not a good image to project," he said.