I have an MSI 970A-G45 and I believe the temp2 on my system is the NorthBridge Chip. It gets hotter than anything else. My research shows it to be the memory and grahics controller and is typically the hottest spot on your motherboard. Mine idles at ~48C peaking to ~62C when encoding a ten minute video. I thought about getting a small fan to blow on the heatsink. The fire icon in speedfan is a user adjustable parameter, so don't get too worried, i read some people reporting NB temps above 80C. If you look closely on your MB you should find a heatsink with NB in small white lettering next to it, stick a fan on it like the antec spotcool if your still curious.
The problem I have with SpeedFan is that it takes its temps relative to the sensor type that I can only seem to change with Hardware Sensors Monitor (HSM). If I change sensors 1 or 2 to diode or transistor the temps are around 95C. If I change sensor 3 to diode the temp is 36C but with thermistor it's 76C. But what's odd is SpeedFan's temps are immediately affected, which I wouldn't think would even be related since both separate programs have their own separate sensor settings. I don't know what the temps pertain to either since, in HSM anyway, I can choose from different labels (CPU, CPU1, CPU2, M/B, PSU, Power, Chassis, Mainboard) for each sensor and the temp doesn't change when I choose a different label. (Some of the labels also seem redundant like M/B and Mainboard, and PSU and Power.) I just don't understand why it's so hard to determine what the sensors are and why the labels are so vague in SpeedFan as "Temp1", "Temp2", and "Temp3" and, in HSM, can be several things. So damn confusing!