The embodiments of the invention in this disclosure describe techniques for early warning of degradation in NOR Flash memories by estimating the dispersion of the threshold voltages (VT's), of a set of NOR Flash memory cells during read operations. In an embodiment invention the time-to-completion (TTC) values for the read operation for the memory cells are used as a proxy for dispersion of the threshold voltages (VT's). If the measured TTC dispersion differs by more than a selected amount from the reference dispersion value, a warning signal is provided to indicate that the page of memory has degraded significantly. Higher level components in the system can use the warning signal to take appropriate action. Since every cell's VT position in an ideal distribution can be estimated, the data from each cell can have a confidence level assigned based on deviation from the mean of an ideal distribution.