The maximum amount of power emitted from a WiFi radio in the US as regulated by the FCC is 0.071W. You're not realistically going to notice much heating from WiFi. Have you ever tried to cook something on the antenna of your WiFi? Try putting a cup of water next to your WiFi router and measure the temperature difference. You'd need massively super-human levels of sensitivity to begin to notice any warming effects. Sure, if you crank the output up to a few dozen watts you'll definitely start feeling the effects of RF. Get it a few dozen watts higher and you'll be at risk of getting RF burns after some prolonged exposure. Get it several hundred watts higher and you're cooking a dinner in the metal box.

As for possibly almost seeing things like WiFi, that's also pretty preposterous. WiFi operates at 2.4 or 5.8GHz. Your eyes start to get sensitive EM waves at about 4000000000GHz (lower end of what is commonly called visible spectrum). Even if you were at the ultra extreme low end of sensitivity, you still wouldn't really be anywhere near the frequency range required.

So for your example of standing in a fire or having a spotlight on your face, you'd need for it to be a practically room temperature fire or a millionth of a candle spotlight. The scales you're comparing to are just silly to the point of being meaningless.