Heavy rainfall is often associated with high temperature because

Heavy rainfall is often associated with high temperature because warm air is capable of holding more moisture than cold air. When air temperature increases, the capacity of the air to hold water vapor also increases. This means that warm air can hold more moisture than cold air. As warm air rises, it cools down and the moisture it carries begins to condense, leading to the formation of clouds. If the temperature and humidity conditions are right, the water droplets in the clouds will grow in size and eventually fall to the ground as rain. Therefore, areas with high temperatures can experience heavy rainfall because the warm air in those areas can hold more moisture, leading to the formation of clouds and eventually, rain.