You can specify dynamic data source for Carousel widget. That means the carousel will retrieve images from database or nanoflow. To make it dynamic, just update the your image storing entity with the new image. Implement a logic that when temperature value rises above a particular level, update the image stored in database. This will refresh UI also with new images.
Here are links to docs about carousel
https://docs.mendix.com/appstore/widgets/carousel
https://github.com/mendix/widgets-resources/tree/master/packages/pluggableWidgets/carousel-native
For storing images in database, please refer to
https://docs.mendix.com/howto/data-models/working-with-images-and-files