What you could try to do is print out the path to the rasters that crash during:
sumDT + dTTemp
Then try to load these 2 files into arcmap, and try and Raster calc them manually (Or whatever that line of code does), and see if you get a better error message or if Arc crashes.
If Arc crashes, its likely an issue with your input data / possible data format limitation.
e.g. if you are trying to add 2 tiffs, from different extents, the resulting file may exceed the maximum TIFF file size / maybe an individual calculated cell value, ends up larger than the range the TIFF format allows. (Guessing without seeing your data!)