Macbook pro 2018 with Mojave overheating when connected to external monitor I'm on a MacBook Pro (15-inch, 2018) with Mojave 10.14.1. When I connect MBP to a external displays (either via HDMI or via Thunderbolt 2 adapters), the temperature raises sensibly (i.e., CPU temperature lies constantly over 90°) and fans start running fast (i.e., more than 50%) frequently, even if I am doing very simple tasks (e.g., writing in Word with a couple of Chrome tabs open with stackoverflow).

I'm not sure that the problem started with Mojave or if it isn't actually related to the OS version.

I'm wondering if there is a way to limit this annoying overheating as well as fans activity, while using external monitors.
The higher power GPU in some MacBooks Pro puts out a lot more wattage than the low power GPU. 

The reason it gets so hot when hooked up to a monitor, even when you’re just running Word or Safari, is because the display outputs are hardwired to the dedicated GPU - if you’re using an external monitor, the dedicated GPU (graphic card) is in use regardless of how demanding the workload is. This puts more stress on the cooling system, resulting in higher-than-average temperatures ;)
Thats the reason. I tried all my 6 Macbook Pro's and all does the same behavior. Switching to the dedicated graphic card and you can't just use the integrated iris.