Why are the average temperature in the middle of the United States warmer than the coasts?

The average temperature in the middle of the United States is warmer than in the coasts due to the thermoregulatory effect of the ocean with respect to ambient temperatures: water tends to gather heat in winter, raising temperatures; while in summer it does the reverse, that is, it cools the temperature. In this way, coastal climates are much more temperate than continental climates, where the minimum and maximum temperature peaks are much wider.

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