The temperature of a large body of water can have a tremendous effect on the air temperature of nearby landmasses. We tend to think about this during the summer when it is often cooler at the shore. However, this is not a phenomenon that is exclusive to a single season. For example, yesterday, the air temperature at my son’s house in North Haven was 56º at 1:00 pm. At the same time, the air temperature at my station located on the beach in East Haven was 43º. A thirteen degree difference over about 8 miles.
The temperature of the water in the Sound is currently a “not-so-swimmable” 41º. As air is transported over the cooler water, the air itself is cooled. The opposite modifying effect happens quite often. For example, if the Sound is warmer in relation to the air around it, the temperature of the air is warmed. This often results in rain or mixed precipitation here at the shore when it is snowing not far inland from here.
Lastly, depending on the direction and intensity of the wind, this modifying effect can exist over several miles, only a couple hundred feet or not at all. For example, if a strong on shore (out of the south, thus over the water and onto land) wind is in play, the modified air can be transported well inland. However, if there is an offshore wind, there may be no difference between temperature observations at the shore and those inland. Finally, if the wind is calm, there may be a modifying effect, which is quite profound over only a couple hundred feet. It is not uncommon to see a 10º - 15º drop in temperature, accompanied by a dense fog layer at the immediate shore when traveling from just a few blocks north of the beach. This often occurs on an unseasonably warm spring day when the air is still, and a 20º – 30º gradient between the air and Sound temperature exists