Why iPhone 13 Pro screen become dark and dimmed on direct sunlight?

There are two reasons:

• It's the direct sunlight
• It's the temperature outside

The iPhone automatically starts to shutdown features when the temperature is outside of environmental temperatures 32º to 95º F. If the humidity is very high and the temperature is above 90F, the screen starts to darken to save the components from overheating. Move indoors and the screen brightens.

The car's environment is the same as the outdoor environment but worse if your A/C isn't working.

Hi there,

If the interior temperature of your device exceeds the normal operating range, you might notice the screen start to dim in an effort to reduce the interior temperature. This keeps your iPhone's components safe and operational.

If you believe this is occurring when it shouldn't, contact Apple Support.

That is because the auto brightness sensor it’s on and detects that is to bright , you can turn auto brightness off and set manually the brightness in your iPhone in the way you want, go to settings/ accessibility/ display and text size/ auto brightness then disable it, go to control cdjtegg etc and mov en tudd es slider of brightness in the way you want and that stays without increasing when in sun light outside