Temperature monitoring?

Hey - just got a 2014 MBA and have 2 27" monitors hooked up while the MBA screen is also on. I have noticed that during regular low CPU activities (browsing etc) that the keypad near the top of the keyboard gets warm. I don't think it's a big deal right now but would like to know:

1) What are the acceptable operating temperatures of the 2014 MBA?
2) What is the best application to monitor temperature or other pertinent metrics?

Thanks