Thank you for your answers that allowed me to find the solution.
So no need to bother with sensors!
In the thermal study tree, in the result folder, right-click on the graph you are interested in, select "probe", in options: "At the location", then click on the (or nodes) that interest us), and in Report option you just have to click on the icon on the right "Answer", The time it loads we get a beautiful curve (or curves) depending on the weather!