In principle if there is a dataset with enough resolution it should be doable. This one had a spatial resolution of 250m x 250m which is why it doubles as a plot of the elevation so well.

In general datasets like this require quite a bit of extra effort to put together since regular measurements for long time periods are not always present in regions with difficult terrain. So for this dataset the group had to do a fair bit of gap filling and spatial interpolation for missing measurements.

Such a high resolution isn’t entirely necessary for large scale weather forecasting so it’s mostly intended for researchers. Sorry for going off on a tangent here but TLDR: yes if someone has put together a similar dataset for all of Austria which I’m not aware of at the moment (would have to look it up)

Of course you can absolutely compute the mean annual temperature even with a low resolution dataset as well if the temperature values are all you’re interested in.