Usually the warmer temperature is either out of consideration to other customers or someone specifically requested it. I don't know if this is correct or not, but the temperature in one cabin is the same as the entire aircraft..

So it might be someone's baby or someone in their advanced years that is feeling chilly, and that's why they reduced the temperature.. You can always ask them to make it colder.

Usually the standard operational temperature onboard SQ flights is around 23C..

I usually feel warm too, and I asked them to lower the temperature because I sweat a lot if I'm hot..