Why are the beaches that located on southern shore of long island often considerably cooler than nearby inland locations hot summer afternoons?

The land heats quicker than water. During a sunny summer day, the Earth's surface receives energy from the sun. Land takes in sunlight and warms up quicker and reaches higher temperatures than water, which has a higher heat capacity. This means water takes more energy to warm up. For this reason, the land near the beach heats up rapidly, while the nearby ocean's water remains at a cooler temperature.

Sea breeze. The difference in temperatures between the land and water bodies generates a sea breeze, which is a gentle wind that flows from the cooler water to the warmer land during the day. As a result, coastal locations like the beaches on the southern shore of Long Island often experience cooler temperatures compared to inland areas on hot summer afternoons due to the cooling effects of the sea breeze.