Q: New Macbook Pro 13" is Heating Up!

Update your OS X software to v10.11.4 then see if it still heats up.

Click your Apple  top left in your screen.

From the drop down menu click About this Mac

Make sure the Overview tab is selected then click Software Update.

Your Mac may restart several times during the update process. That’s ok.

And make sure your Mac is well ventilated >  Mac notebooks: Operating temperature

Install a temperature and fan speed monitoring app to see what is going on. I use Macs Fab Control there is also iStat and others too.

When hot take a screenshot of the temps and fan speed and post it here

How to take a screenshot on your Mac - Apple Support

If you are displaying Flash content on the internet heating up is not unexpected.

Perform a SMC reset:

https://support.apple.com/en-us/HT201295

Install a temperature/fan speed monitoring application as suggested by Illaass.

Open Activity Monitor to ALL PROCESSES and set CPU to display values from high to low.

When your MBP gets hot, post images of both for review.

Ciao.

Apps can affect Mac performance, battery runtime, temperature, and fan activity - Apple Support

Here are a few fan and temperature monitoring apps as recommended by Illaass.

Fan speed monitoring apps:  Macs Fan Control  or  iStat Menus 5 

or  smcFanControl 

Kim

Install a temperature and fan speed monitoring app to see what is going on. I use Macs Fab Control there is also iStat and others too.

When hot take a screenshot of the temps and fan speed and post it here

If you are displaying Flash content on the internet heating up is not unexpected.

Also take a post a screenshot of CPU window in Activity Monitor with View All Processes check and COY sorted with highest CPU at top.

50 C (122F) seems like a very reasonable temperature.