I don't think it is necessarily the temps themselves, but the pattern.... if they stay above your normal LP temps (like Susannah said) then I'd say thats a good sign. Also, some people never have temps reaching 37, especially if they do oral temps... mine are vaginal (yes, very glamorous!) so they tend to be higher than oral temps.

The temps for this cycle (with my BFP) are in my sig. if you want to have a look...