What specific brand your RX 470?
Software monitor usually at +- 10C error threshold readout, just to be safe you'll have to assume its already at 91C. Meanwhile you can do this
- max out case fan, either add fans or replace with known good review fan.
- replace thermal grease with known good review thermal grease.
- if you have experience with digital multi meter, you may re-check power delivery at graphic card copper lane PCB, 6 or 6+2 PSU header and connector, PCIe 16X slot.
- learn how to use MSI afterburner.