Source: WeatherSTEM
Mountain and valley breezes are another example of thermal circulation. During the day, sunlight warms the land and air in the Valley. This less dense air rises along the valley walls in a gentle upslope wind, known as a valley breeze. The flow reverses at night as air on the mountain slopes cools quickly. This denser air flows back down the slopes of the mountain and into the valley. This is called a mountain breeze. These breezes are best felt on clear, summer days when the prevailing winds are light. In the Northern Hemisphere, valley breezes are more obvious on south-facing slopes due to the increased exposure to the sun.