tl;dr; Futurama was right: nuclear winter cancels global warming
1. At high humidity max temperatures humans can survive for more than 30 minutes are not that high.
2. During a heatwave (peak 46C at ~50% humidity) in India 30% of Ahmedabad all cause mortality was connected to temperatures https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4024996/
3. Temperature increase is not going to be the same across the globe. Many models predict with a 2C global avg temp increase a 4C increase of average temperatures in India and Pakistan with peak temperatures during heat waves going up by as much as 10C.
4. That temperature increase pushes conditions beyond what most people can acclimatize to. In large areas of India, Pakistan and China (among other places) physical labor and maybe even survival without access to cooling will not be possible for as much as 20-60 days per year.
5. A significant chunk of 3.9B people living in India, Pakistan and China will be displaced with nowhere to go. All 3 countries have nuclear weapons to make sure they have somewhere to go :P