Sounds like a glitch, and/or its reading the wrong sensor. If it was a real reading it'd bounce around a bit. And it also might not be so suspiciously divisible by 8.
Double-check it with Realtemp or HWMonitor.
Other programs report stable temperatures at about 30C, and no absurdly high temperatures anywhere, so I guess it's just some sort of weird SpeedFan bug. Thanks for the ideas on alternative temperature chekers!