That's how most cards work, you know.
Never noticed how pro overclockers on air beat people with water cooled cards?
Unless your video card is overheating (which would be well over 80C), only a very significant reduction of temps (towards 0C) would noticeably expand overclocking headroom.
At ambient temps your card will likely stop scaling with voltage before it reaches this thermal threshold.
You may gain maybe 25-100MHz depending on temperature difference. But in most cases the difference is not mind blowing.
Low temperatures for longevity and absence of noise are more important factors to consider here.
Edited by zalbard - 2/20/13 at 10:34am