It's relative to the 'importance' of the run... an 'A' race i'd have a bag and warm clothes for after, Parkrun not. It's not during the run part that the cold gets me so much, it's any standing around so I just layer up for that. 6ft2 and 68kg = no insulation.
I was also taught a lesson by a clubmate in vest and shorts today. It makes me wonder if it is worth risking