I use my own tolerance for the hot or cold weather. We now do our morning walk about 6:30 A.M. BEFORE the heat starts to get unbearable here in Florida. That we we can get our full mile in. At night we wait until between 7:30 P.M. and 7:45 to go so we get another mile in. The kids can tolerate those times great. I think if I'm terribly uncomfortable they must be too?? I do the same with the cold months here. If I am freezing cold with the wind bothering me, they must be too so I shorten the walk. It seems to be working for us.