Why does my MacBook Pro (15" Late 2011) get hot in different locations in the house?

When I have it in my room it's maintains a cool temperature; but when at the desk, it gets extremely hot. I'm using Wi-fi.

Could it be the environment? The room is dark while the desk/office area is typically brightly lit.

Could it be the distance from the wi-fi access point? The wi-fi strength meter is always full although the room is closer to the access point than the office.