Abstract: In this fast and growing age large amount of data is generated and save or store somewhere daily. These data are included many information. They may be financial data, scientific, medical science related data, engineering data and many other types of data. Analyzing such data is an important need. Data Mining is a technique which providing tools to discover knowledge from data. It includes so many techniques for KDD such as classification, clustering, regression etc. In this paper a comparative study of C4.5 and Naïve Bayes Data mining classification techniques has been done. The experiment is based on weather data. That includes parameters like temperature, humidity, wind speed etc. Weka tool is used here for the experiment. Keywords: Data Mining, Classification, Naïve Bayes, C4.5.