A series of data set of ocean wave records from the Pacific Ocean and the Sea of Japan is analyzed for understanding freak wave characteristics in lights of wave height statistics, frequency and directional spectrum parameters, and nonlinear statistical parameters. In addition, measured maximum wave heights are compared with predicted ones by a nonlinear wave theory, and the relation of freak wave occurrence with weather condition is made. It was found that observed data shows a weak correlation between maximum wave heights and kurtosis of free surface elevation and that freak waves at peak of storm are observed under migratory low atmospheric pressures.