After our return flight from Turkey last Friday, I'd say
always carry something to layer. We got two seats at emergency exit which I thought was great for the extra legroom, but it was
freezing. I have never been so cold on a plane and of course was wearing lightweight clothes. Fortunately I had put a shirt in my bag as a precaution but it wasn't warm enough & my sockless feet were like 2 blocks of ice by end of 4 & half hour flight
I did mention to stewardess but no change & no blankets are carried on short-haul flights now.