This article provides an overview of Japan's climate and discusses the rainfall during the four seasons. Summertime is usually the rainiest season in Japan, with frequent downpours that can last for several days at a time. Factors such as typhoons, monsoons, El Niño/La Niña cycles and ocean currents affect rainfall levels throughout different areas of Japan. Heavy rains can cause flooding, mold growth and health problems. Understanding what causes rainfall patterns helps people better prepare for extreme weather conditions.