I use
dark library to match darks to lights, download
here. In this they say that the EXIF is not necessilary the best match to the actual sensor temp but probably the best that can be had.
The other issue is that EXIF temp is generated at the start of the frame so a long frame may see it heat somewhat and EXIF may not be assurate.
I find EXIF temp to be a reasonable match and temps don't rise that much during subs unless the ambient changes somewhat.