Hi,
The short story is you are EXACTLY where you should be. I got the same in Prime95.
More:
The max rating for that CPU is 105degC I believe, and going over 60degC is not only perfectly safe but NORMAL so St0rm_kill3R is misinformed completely.
I have one of the best coolers (Noctua NH-D14) which should be roughly similar to your cooler, and get the following temps:
a) 28degC (idle in a cool room)
b) 40degC+ (under LOAD in games etc)
c) 66degC (Prime95 stress test)
If I OVERCLOCK the CPU then the Intel Power Management doesn't work properly and at 4.5GHz the temperature goes as high as 90degC (though it still works and it's way higher than it would be in a game). Since very, very few games benefit from an i5-3570K overclocked beyond 4GHz I go to the max frequency that allows me to keep the CPU as cool as possible. So...
I use 4.2GHz and can achieve that by this method:
1) click "XMP" to optimized defaults (thus Intel Power Management keeps power/heat reduced)
2) change to Manual, then set each core Multiplier to "40" (start low to test then raise. I got 42 but not 43. Your motherboard will have some affect on this as will how good your CPU is.).
3) verify DDR3 settings are correct (i.e. 1600MHz not 1333MHz if you're rated at 1600MHz). Manually correct if need be but preferably done automatically.
4) run both MEMTEST and Prime95 (Intel also has a diagnostic tool). www.memtest.org