Irish temperature immunity

Irish people seems to be absolutely immune to any changes in temperature.

The girls don’t mind running around on weekend nights in January with short skirts and tops.

But even more confusing: today was a lovely warm spring day and the sun was shining with at maybe 18 degrees Celsius – but I was the only one who felt so warm that I was running around in T-shirt.
The native Irish where still wearing jackets and some even seemed to be freezing…