The man was struck by the tree when it fell during high winds in Kings' Park in Retford, Nottinghamshire, at 13:50.
Nottinghamshire Police confirmed the man, whose age is not yet known, had been riding through the park on a mobility scooter when he was hurt.
Paramedics attended but the man was pronounced dead at the scene. The local council said it had closed all of its parks as a precaution.
The tree, believed to be about 40ft high, fell directly on to a path.
Speaking about the park closures, a spokesperson from Bassetlaw District Council said: "We apologise for this inconvenience, however the safety of the public is of paramount importance and we would ask all residents to avoid these areas."
Several other parks in the Nottinghamshire area were closed on Thursday as strong winds battered the region.
Rufford Abbey Park was closed because of falling trees while Wollaton Park and Newstead Abbey were closed because of safety concerns.
Elsewhere in the East Midlands, fallen trees continued to cause disruption on roads and railways and three lorries overturned on the M1 motorway.
More than 11,500 homes were also left without power.
Michael Clarke from Western Power Distribution said: "We have got everyone we can out dealing with the incidents.
"We continue to work extremely hard in difficult conditions to restore electricity to these properties as quickly as we can and will do so until all have their power back."
In Lincolnshire, the Environment Agency issued 31 flood warnings across the region with around 18,000 homes in Boston said to be at risk of flooding.
A man has died after being hit by a falling tree.