Once you've been treated for heat stroke in the hospital it can take 2 days to start recovering from the heat stroke.
Those 2 days will be initial recovery in the hospital and then it can take a couple months to a year to fully recover from the heat stroke once you've been discharged from the hospital.
Heat stroke is a very serious health issue and can be deadly if not treated so avoid the heat as much as possible and stay well hydrated.
Drink water or some other liquids that can hydrate you even if you don't feel thirsty.