We live in central Maryland where the temps right now are in the 80's (90 on Wednesday) and the humidity is coming back. We let our bullies out in the yard and their activity is limited to going potty when there is high heat a humidity. Then back into the house for water. Our vet drilled into our heads that bullies do not do well in heat. If there is a walk, it will be in the early morning.
When the temperatures are hot, we walk early in the morning, and again later in the evening when temperatures are a cooler. During the day it's out just to do potty.
On the weekends I'll take them out around 6:45am-ish, and we usually walk for 20minutes. On weekdays we'll do it around 7pm, maybe for 15-20 min. Doesn't need to be a long walk at all...sometimes we just go to the corner and back. The humidity has been bad for us here (well, for CA anyways), and it's supposed to get to the upper 90's/low 100's this week!
We try and walk every evening and if needed we wait until 9pm to go when the temps have dropped into the low to mid 80's. If it's warmer than that, we won't go. Our walks are about a half mile or longer in the winter and our pace is very slow. Mine usually don't even pant...it's that strenuous! Lol
We have an 11 yr old who lays around all day and we feel that these regular walks are important to get her up and moving. I also have a 7 yr old who runs and plays all day so she may not need them but she loves it.
I do not walk Elmo, he gets plenty of exercise on our 2/1/2 acres of land. He only goes out to get exercise when it is not hot, Elmo gets a lot of exercise running around the house playing with all of my others 4 legged babies.