The dog was found unconscious and convulsing at the FDR State Park in Yorktown Tuesday afternoon.
The dog died of heatstroke.
The temperature inside the van reached 140 degrees.
Authorities say 41-year-old Heriberto Palacio, of the Bronx, is charged with animal cruelty.
He said he left the dog inside the van so he and his girlfriend could go for a swim and have a barbecue.