Flow ratings are divided into two categories: strength and skill. A channeler's strength is determined initially and will not change, but his or her skill is continually increasing. Flow strengths range from 1 to 35 for each flow and are more important for weaves that rely on brute strength with the One Power. The max flow skill of channeler is determined by a combination of their strength in that flow, and their training level. Flow skills will increase with usage and observation of that flow.
Weaves require a certain amount of strength and skill in flows in order to learn and weave them. The strength requirement must always be met, but it is possible to learn and attempt to weave something that is slightly beyond a channeler's skill level, though it will significantly increase the risk of burning out.