I have a variety of raster files from the exact same study area including different values (hourly mean radiant temperature). Is it possible to find out the overall min/max values (not each individual one)?
You could use Statistics for rasters tool (in
Processing Toolbox | SAGA | Geostatistics).
It will give you
Maximum raster, each cell represents the minimum and maximum value across the layers. (There are also
Arithmetic Mean etc... if you like).
If you want to have single overall
maximum value, next step will be Raster Layer Statistics tool (in
Processing Toolbox | QGIS - Raster Analysis). Give
Minimum raster from above operation to this tool, then
MIN value is the overall minimum.