The data used to produce these plots are
**provisional**
and have not been reviewed or edited. They may be subject to change.

## Duration Curve For Period of Record

## Notes

Duration curves (or cumulative frequency curves) are constructed by ranking all values for a given period from largest to smallest, and assigning a percentage exceedance to all values relative to the largest value.

Ordinary-least squares (OLS) regression is used to compute the values, having been determined to be the most appropriate regression technique. Like all regression techniques, the true relation of the response and explanatory variables is unknown and the regression model is only an estimate of this relation. Other regression techniques might yield different models and therefore, different duration curves. The differences between regression techniques typically are within the 90-percent prediction interval of the OLS regression represented by the gray shaded area.