I'm sometimes given to fainting, and not always from low blood sugar. (To be sure, I have rarely actually fainted because I usually realise what's going on and can sit down in a safe spot in time.) During the summer, it regularly happens to me that for a day or two, I tire out very quickly and may become faint-prone, then start wondering what's wrong, then stop wondering when I hear that an ozone pollution alert has been issued. So the concept of health weather forecasts makes sense to me.