Bodies of water take longer to heat up and cool down, so absorb all the heat through the spring and summer months, when the sun is at its strongest, and then lose that heat slower through autumn and winter, once it starts cooling down. For land on the other hand, it heats up and cools down much quicker.

Beaches often feel warmer than inland areas during winter due to the high heat capacity of the ocean. Water retains heat much longer than soil or rock; as winter sets in, the ocean slowly releases the warmth it absorbed during the summer, acting as a giant radiator for the coastline. This creates a "maritime effect" where coastal air temperatures remain more moderate and stable. While the water itself might eventually get cold, it rarely drops as fast or as low as the air inland, meaning a beach in January will often be several degrees warmer—and much less likely to see frost—than a town just 20 miles from the shore.