He was found at about 3:30 p.m. by a passer-by, who called police.
Officials say it looks like he was just cutting through the park when he was struck.
The man was pronounced dead at the scene.
The victim was identified as Elmaz Qyra, 46, of Brooklyn.
A number of trees also came down onto vehicles on Fifth Avenue.
At least five large trees that had fallen caused traffic problems. One of the trees came down on an inbound Bronx express bus.
Fifth Avenue was closed between 72nd and 66th streets until early evening while those trees were removed.
So many trees and branches came down that the Parks Department advised people to avoid public parks and to use caution near street trees.