Extreme events drastically impact water and energy cycles, and consequently, the foodwebs and human activities. Under anthropogenic climate changes, extreme heatwaves across high-, middle-, and low-latitudes are expected to increase. Understanding the causes and driving mechanisms behind the increasing occurrence of heatwaves is critical. This course is designed for senior undergraduate students and graduate students. The course aims to overview the basic knowledge of extreme definition and occurrence frequency/intensity in the climate system under changing climates. We will also discuss how extremes are formed. Statistical techniques for analyzing extremes will be introduced. Students will read and lead the discussion on several recent papers on the relevant topics, along with analysis of simulations from global climate model large ensembles for the final project.