With planned maintenance notifications for App Service Environment v3, you can get a notification 15 days ahead of planned automatic maintenance and start the maintenance when it is convenient for you. This feature allows you to reduce the potential for service interruptions by giving you notice and allowing you to prepare for and set when maintenance will occur.
See details on the App Service Environment specific feature.
For general background information around improvements to observability and control of planned maintenance activities on the App Service platform, visit the blog Routine Planned Maintenance Notifications for Azure App Service.