I'm sure air conditioning is part of the problem. We never get acclimated.
AC is a big part of the problem. i've been having difficulty increasing my
running distance lately. temps here are in the mid-90's, humidity also
in the mid-90's. i'd start off fine, but would quickly lose steam. i've been
running the AC all day and night, not going out other than to run or to
the gym or to bicycle. so this morning cut the AC when i got up, went
running about 4pm, managed to increase distance by 3 miles. still felt
good at the end, but running gear thoroughly soaked, must have weighed
3 pounds. acclimatizing before exercising made a big difference.
so if you're living with constant AC, why not acclimatize yourself first
before your walks? sit outside in the shade for an hour or so before
the walk. and don't forget to carry your water bottle.