Purpose. We have derived formulas for the prediction (calculation) of daily water discharges during the period of rainfall floods on the rivers of the Northern coast of the Sea of Okhotsk. Methodology and Approach. Averaged flood decay curves in relative ordinates have been calculated for nine hydrological posts. Then, an analytical approximation of these curves has been carried out, and relationships between the parameters of the equations of the curves and various hydrological and morphometric characteristics of the watersheds under consideration have been found. All calculations and graphical constructions have been performed using Microsoft Excel. Results. Recession curves are well approximated by a power function. The indicator of “relative depth of the summer low water” is proposed, which is associated with the degree of flow reduction. District formulas for calculating the hydrograph of runoff during the rainfall decline have been obtained. Using an example of a flash flood of rare frequency it is shown that for the studied river the average relative error is 8.4%, and for the unexplored one it is 16.8%. Theoretical and Practical implications. This technique will be useful for hydrologists-forecasters and specialists conducting engineering-hydrometeorological surveys.