Verstappen started a lowly 16th in China after an engine problem in qualifying meant he was unable to make it out of Q1.
Chinese Grand Prix driver ratings
But the Dutchman again showed his class in tricky conditions on intermediate tyres, passing nine cars during the opening lap and moving up to third before the track dried enough for an early switch back to slicks.
The 18-year-old has previously starred in the wet, including in last year's Brazilian Grand Prix, in which he charged from 16th to finish third.
"He appears to have an almost sixth sense in the wet," said Horner.
"He doesn't seem intimidated by it in any way, and is prepared to explore all the boundaries of the circuit available, to find where the grip is.
"There was one move he made on the outside of Turn 6, where he went straight down the outside of two or three cars and then cut back, and it was very, very impressive."
Horner believes his young star is "right up there now" among F1's best-ever drivers in the wet.
"It is not a coincidence now," he said.
"You can see Brazil wasn't a one off, and that maybe good old Bernie [Ecclestone]'s sprinkler system would be good for us.
"The way he has grown up driving go karts in the wet on slick tyres and stuff like that, he has developed a real instinct and feeling.
Read the full article on eurosport.co.uk: Horner: Verstappen has sixth sense in the wet