In winters, it is often warmer in San Francisco than in nearby Sacramento, \({\rm{150 km}}\) inland. In summers, it is nearly always hotter in Sacramento. Explain how the bodies of water surrounding San Francisco moderate its extreme temperatures.

Waterbodies like rivers, lakes, and the sea affect the temperature of nearby land. Water takes more time to get cool and hot when compared with the air on land. So, during winter, a warm breeze from the water bodies makes San Francisco warmer. This process of heat transfer that occurs between fluids is called convection.

This effect will decrease as it moves away from the water bodies. That is why San Francisco has a warmer climate than Sacramento, which is away from the water body.

The temperature in San Francisco is closely controlled by the surrounding water bodies. As the waterbodies slowly attain heat and cold, they transfer their temperatures to the land. So, during summer, the land becomes cool, and in winter it becomes warmer.

Thus, waterbodies maintain the temperature in San Francisco through the transfer of heat by convection.