When I try to display the Rainfall in an entity card, displaying either rainfall_lasthr or rainfall_lastamount it displays a value Unavailable.
What am I doing wrong?
Is the rest sensor itself even working? That is, does it correctly store all those attributes?
The template sensors are either not working because the rest sensor’s attributes are missing, or because that value_template is wrong - you are trying to access a JSON structure that isn’t there, and there is not attribute “WS_Rain”.
I would suggest trying the new rest integration syntax where you can directly specify the sensors you want. Something like this:
Ok, I tried that syntax, but it didn’t work as I failed to mention the YAML was in my included sensor.yaml file, rather than configuration.yaml so the topology(?) wasn’t correct. However after you sort of nudged in the right direction, this worked: