The temperatures that your case is posting don't really tell us anything. They are a way for you to recognize that something is wrong.
You should download and install HWMonitor
HWMonitor will show us the Minimum/Maximum/Current temperature of your CPU/Motherboard/Video Card/Hard Drives if the components have the sensors.
After you have installed HWMonitor, start the program up and leave it running. Then you just need to play your game until it starts to lag, but before it crashes. When you exit the game you need to take a screenshot of the HWMonitor window and post it. Here's a guide to posting a screenshot if you need it.