Computer Temperature Spikes Please Help

Hello,

I currently built a new system with the following specs but occasionally when i start to game it alt tabs itself to tell me that the system is 90 degrees then i can go back into a game for a few more minutes and it tells me again that im over heating,

Here are my specs,

intel i7 950 3.06g
asus rampage 3 formula R motherboard
12 gigs corsair 1600 ram
asus eah 6870
corsair 800w power supply

Any help would be appreciated :)