We developed a method to predict heavy rainfall in South Korea with a lead time of one to six hours. We modified the AWS data for the recent four years to perform efficient prediction, through normalizing them to numeric values between 0 and 1 and undersampling them by adjusting the sampling sizes of no-heavy-rain to be equal to the size of heavy-rain. Evolutionary algorithms were used to select important features. Discriminant functions, such as support vector machine (SVM), k-nearest neighbors algorithm (k-NN), and variant k-NN (k-VNN), were adopted in discriminant analysis. We divided our modified AWS data into three parts: the training set, ranging from 2007 to 2008, the validation set, 2009, and the test set, 2010. The validation set was used to select an important subset from input features. The main features selected were precipitation sensing and accumulated precipitation for 24 hours. In comparative SVM tests using evolutionary algorithms, the results showed that genetic algorithm was considerably superior to differential evolution. The equitable treatment score of SVM with polynomial kernel was the highest among our experiments on average. k-VNN outperformed k-NN, but it was dominated by SVM with polynomial kernel. 1. Introduction South Korea lies in the temperate zone. In South Korea, we have clearly distinguished four seasons, where spring and fall are short relatively to summer and winter. It is geographically located between the parallels 125°04′′E and 131°52′′E and the meridians 33°06′′N and 38° 27′′N in the Northern Hemisphere, on the east coast of the Eurasian Continent, and also adjacent to the Western Pacific, as shown in Figure 1. Therefore, it has complex climate characteristics, which show both continental and oceanic features. It has a wide interseasonal temperature difference and much more precipitation than that of the Continent. In addition, it has obvious monsoon season wind, a rainy period from the East Asian Monsoon, locally called Changma [1], typhoons, and frequently heavy snowfalls in winter. The area belongs to a wet region because of more precipitation than that of the world average. Figure 1: The location of South Korea in East Asia and the dispersion of automatic weather stations in South Korea. The annual mean precipitation of South Korea, as shown in Figure 2, is around 1,500？mm and 1,300？mm in the central part. Geoje-si of Gyeongsangnam-do has the largest amount of precipitation, 2007.3？mm, and Baegryeong island of Incheon has the lowest amount of precipitation, 825.6？mm. Figure 2: Annual (a) and summer (b) mean
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