How in the heck were you able to function without the windows being open? That sort of thing kills infants and pets...
The first summer I had to do that I lived 15 minutes away from work. Work was about five minutes from shopping. So, in the morning and evening it was tolerable for that amount of time. During lunch I could get where I was going and back without sweating too much.
The second summer though, I had a new job that was 45 minutes away. I had to show up in the early morning so not bad. But I left at 2pm so it was murder at that point. I froze a water bottle at work and by the time I got home had drunk it all.
I eventually changed my shift so that I started work at noon and left at 10pm, 4 days a week. Going to work without it being too hot and then leaving after the sun was down. With no traffic either way I got to work and home faster as well.
At a certain point though you reach an equilibrium where you aren't going to get any hotter. It's kind of like the inverse of being in an ice bath. Eventually it gets warm and you're okay.
There was one point though where I think it very nearly could have killed me. One of those 120º days I think.