The service will run until its last departure from the library bus lay-by at 11.07am. The earlier finish is intended to help protect both the driver and passengers from the heat as temperatures rise towards the hottest part of the day.
Overton Parish Council has apologised for any inconvenience caused by the change.
The council said the priority is to ensure everyone using the service remains safe and well during the hot weather.
Passengers are advised to plan their journeys accordingly and allow extra time if they need to make alternative travel arrangements.