Coastal communities often experience milder winters and cooler summers

This is because water has a high heat capacity and therefore acts as a temperature buffer. Water takes more energy - compared to most materials - to raise its temperatures by one degree. This means that during the summers the ocean water remains relatively cooler than land. This is why coastal communities are relatively cooler due to the cooling effect of the oceans.

Conversely, during winter, it takes more time for ocean water to lose most of the energy it had absorbed to drop its temperatures (compared to land). The oceans remain relatively warmer than land. Coastal communities, therefore, feel relatively warmer in the winters.