However I realized that the temperature difference between the original epw and the morphed one reaches -10 C at night time. As far as I know, the heat island effect is amplified during the night. So the morphed file should never contain temperatures below the original one.
Do you have any idea why this might be the case here?
A -10C difference is very odd and I can’t think of any explanation off the bat. What EPW are you using and are you changing the city parameters at all from the example file? If so, upload a GH file and we can check it.
I am attaching the gh file here. The location is Ankara - Turkey.
I also used the XML file generated by this GH file and used in to run on UWG. I am also sending the original and generated epw files. The results vary between -11 and 4 degrees. So I am getting similar results from both.