Query Multiple Machines to obtain Max/Min of a metric

I am new to grafana and I am getting some basic panels going on my end.
Currently, I would like to look a group of machines (all nodes in a compute cluster).

For example, show the max temperature among all these machines.

Right now, I have a comma separated dashboard variable that has all the hostnames and I can dynamically select a single instance via the panel using the following query.


My goal is to get the max(metric) , across a collection of nodes. How would one achieve this?
A simple example, would be to grab the max temperature across an entire set of nodes.