Cold weather is supposed to be better on your lungs, hot weather you obviousy sweat more. Beside that I'm not sure.
If you can get through a training session in a cold enviornment, mentally, you will be better prepared for other things knowing you were able to push through that.
I know I always get a sense of satisfaction sticking through a full set of sprints out in 20 degree weather when I could have taken the easy way out and cheated myself out.
Same here man i did roadwork at -20 degrees celsius. My sweat was freezing as i sweated more. i was running looking like terrorist with the ski mask but afterwards i felt invincible.
my club i train in is always below zero degrees even with a space heater on so i must have a huge advantage training in the cold everyday