Boss knows about my heat problem and I'm the only one who has to work outside in this 35° Celsius heat!

I hate it. I go to a specialist for it, boss knows it and he always makes me work outside, as only person and is suprised in shaking, dizzy, visibly in pain, slow reactions, loss of feeling, etc. But no, I have to work outside as only one. I hate it. I know I'm going to be a zombie for the next few days.