Thank God for Sun- Brella!I drank about 8 20oz. bottles of water Thursday and with a nice breeze, I was fine.As far as a 10-100. Didn't come till about 6 pm.Those days when there is no breeze they really get tough.Being dark complected helps.I've always stayed active outdoors and know when to take breaks and hydrate.Folks on certain kinds of meds have to really be careful!I also try to keep a cool wet towel in my cooler to put on my head or around the back of my neck!