How can I know my phone temperature at all times on the iPhone 8

There is no app for that that I'm aware of. I suppose you could tape a thermometer to the phone if seeing its temperature is important to you? Unless your iPhone is overheating (you'd see a warning message if it really does overheat) or having some temperature related operational issue, I'm not sure what is to be gained by being to constantly see the temperature of your iPhone.

talyn51 wrote:

How can I know my phone temperature at all times on my iPhone 8

Carry an infrared thermometer with you at all times.