I find that anything above 80 affects me. I can be sitting outside later at night and once the temp drops below 80 and the sun is down, I can walk sooo much better, it is soo weird. I also found last summer that I can't sit in the sun no matter what the temp is. I can't even sit inside with the sun shinning in on me otherwise I have a hard time getting up and walking. Last year I sat at a state track meet and it was only in the 70's with a nice breeze. I went to get up and walk to the restroom. My husband had to help me out of the stands, I had no balance and my legs didn't want to move---crazy. I always liked going to the pool and laying out. Not last year and I have a feeling this year will be the same.