I got what seems to be ME/CFS at the end of 1989 while living near Toronto, Canada. Over the next 9 years, I spent considerable time in much of eastern and central US and Canada. I felt worse in Toronto/New York area. I felt mildly better in Winnipeg (central Canada - coldest major city on earth, dry, sunny) and in Texas and Florida. I have been back to US and Canada over the years and do not have "well" periods there. I was amazed to find that when I arrived in Cuba I was suddenly back to very close to pre-illness health. Over the next few years, I found this to be the case when I was close to tropical waters. I spent the next 6 years mainly in Buenos Aires, Argentina, but also Brazil. I was never well in Rio de Janeiro and Buenos Aires. I was well at first in Iguazu, Brazil and north eastern Brazil. At that time, the "well" effect stopped working for me - except for perhaps my first few days near tropical seas.