And to add the comment about how velocity is relative, even if you have a large mass of material moving quickly, this doesn't make it hotter. So, velocity isn't by itself the metric you need but variance in velocity, where velocity is a vector quantity. This way you can get a picture of the range of differences in velocity amongst the particles. Temperature is directly related to this (and would only be related to this for simple point masses that only react like billiard balls.)