What would be the ideal temperature for a gaming PC? Mine heats up a lot

My PC, when idle, stays around 30 to 40 degrees. But as soon as I open GTA V, it goes from 0 to almost 100 in a few minutes. I’d like to know if this is normal or if I’m doing something wrong. I built my PC by myself and temperature was my first concern. That’s why I went for:

  • a large case with several outlets for coolers
  • a good quality water cooler
  • good thermal paste on the processor and on the graphics card
  • full case cleaning once a month

And even so, it doesn’t seem to have helped much. Is 70 to 90 degrees a good temperature while playing heavy games? I’m terrified of burning something out.