You can import the data directly into a table field with an independent domain of Cartesian and a dependent domain of Temperature.
If the coordinates in the file correspond to the node locations in the model, set the interpolation method to Nearest Neighbor.
Reference this table field in the temperature load.
The easiest way to create the field is in context. Create a temperatre load, set the distribution to Field and pick the option to create a new table field. There is a button on the table field dialog to import data from a file.