Too chilly for fun!

Yesterday I took S on a field trip at school--we went to our local fairgrounds for Agriculture Day.  It was pretty cool for third graders--they saw demonstrations on tractors, planting, various animals, etc.  However, it was mostly outdoors and it was cloudy and fifty degrees with wind.  Wind chill put us at about forty-five degrees.  Not too bad for your average kid but S has never done well with cold unless he is extremely bundled up.  After an hour he was asking to go home and by hour two I was getting ready to take him to the bathroom so he could stand under the hand dryer :\  Before we went to do that, though, his teacher came up and asked if I wanted to take him home early because she could see his lips were turning blue.  So we went to Tim Hortons for hot chocolate and blasted the heat in the van for about half an hour until he was warm enough to feel comfortable :p

S and Iz are my kids that struggle with the cold.  I wonder if its related to their CHDs?  S's is closed and Iz's big ones are repaired or closed on their own but I still wonder if the struggle with the cold is connected.