Why is it generally cooler along the coast during warm spring days?

     Temperatures at 2:12 p.m. today. It's coolest at the coast. (Image: NjWxNet)

    Temperatures at 2:12 p.m. today. It's coolest at the coast. (Image: NjWxNet)

    It happens every spring at the Jersey Shore. 

    Temperatures spike into the 80s inland, and that immediately sparks imagery of relaxing on the beach in your bathing suit to get your first sunburn of the season while watching the gentle Atlantic Ocean waves lap at the shoreline. 

    But not so fast. (That’s if you don’t mind sunbathing in the much cooler temperatures at the beaches.)

    If you’re a longtime radio listener, the words “cooler at the coast” probably ring a bell, and the temperature differences can be extreme at times.

    • WHYY thanks our sponsors — become a WHYY sponsor

    During the summer, beachgoers along the oceanfront can be enjoying temperatures in the 70s while just inland, everyone else is baking in the 90s.

    Or during the spring, like today, shortly after 2 p.m. it’s 58 degrees in Seaside Heights but 81 just over the bridge in Toms River. Further south in Cape May, it’s 61 degrees but the middle 70s further north in interior sections of the county. 

    It’s courtesy of the sea breeze effect. National Weather Service meteorologist Walter Drag explains that it occurs due to the difference between the warm air over land and cool air hovering over the ocean (currently around 50 degrees).

    “What you have is, when wind increases during the day, cooler air is heavier, and it’s drawn inland, replacing the warmer air that’s rising. Winds can begin westerly, then when the land heads up, turns southwesterly and then southerly,” he says, stating that the air along the coastal areas becomes cool due to ocean air getting pushed along the coast and inland. 

    Sometimes, Drag says, if the offshore winds are weak, the sea breeze can dominate and push as far west as the I-95 corridor or even Philadelphia. The stronger the westerly or northwesterly winds, the less sea breeze inward force. 

    Ocean temperatures are slow to warm and don’t generally reach the 70s until August, so that’s why the sea breeze effect is so dominant through late summer, according to Drag. 

    He adds that even today in Philadelphia, which is far from the ocean, it’s cooler in southern sections of the city due to the breeze coming off the still chilly Delaware River. 

    WHYY is your source for fact-based, in-depth journalism and information. As a nonprofit organization, we rely on financial support from readers like you. Please give today.

    Want a digest of WHYY’s programs, events & stories? Sign up for our weekly newsletter.

    Together we can reach 100% of WHYY’s fiscal year goal