My XPS 13 (9360) heats up when charging.

I've been having some overheating problems with my new XPS 13 (9360), with temperatures across all 4 CPU cores reaching almost 100°C if I leave it plugged in and charging. It's worth mentioning that I don't experience this temperatures when running off battery power; the laptop idles at about 50°C and heats up as I would expect when under duress.

The only way I've found to prevent this and still be able to charge my battery is to use Dell's Power Manager program to set the laptop's Thermal Setting to Cool. Once enabled, temperatures return to normal. However, this is far from a permanent solution because I've found the Cool setting reduces my laptops performance much more than I would like.

Does anyone know what could be causing the overheating issue, and how I could go about fixing it? Ideally I'd like to be able to run in Optimised (or even Ultra Performance) mode 100% of the time without having to worry about heat damage to the CPU.