World and Nation

Don’t Put Away That Jacket Just Yet

Don’t Put Away That Jacket Just Yet

For the rest of the work week, Boston will continue to see slightly below average temperatures, with no dramatic warming trends on the horizon. The reason for these slightly chilly conditions can be blamed on the wind direction. There are three main factors in determining the temperature. The first is the sun. Obviously, it is warmer during the day rather than at night and during summer rather than winter, based on the sun’s presence. The second factor in determining temperature is cloudiness. Clouds can act to block sunlight from hitting the ground, or act like a blanket to trap heat. The third factor is the wind direction. Wind can blow warmer or cooler air into our region. Meteorologists call this phenomenon “advection.”

As one might expect, wind blowing from the north will make it cooler, and wind blowing from the south will make it warmer. But because of Boston’s location next to the ocean, whether the wind is from the west or east is also important. This difference has to do with differing thermal properties of land and ocean. Land (e.g. rocks, sidewalks, grass, sand) heats up very fast when sunlight hits it. The land in turn heats the air very quickly. Therefore, when wind blows from our west, it has passed over the hot ground and will make us warmer. The ocean, on the other hand, does not heat up very fast when sunlight strikes it. This has to do with water’s relatively high heat capacity and density. The ocean remains cold, and so the air above it is cold. When wind blows from our east, we say the cold air is “advected” into Boston. This week the wind will be blowing from the northeast, meaning you should keep that jacket handy.

Tonight: Clear. Low 48°F (9°C).

Tomorrow: Sunny. High 66°F (19°C).

Tomorrow Night: Partly clouds. Low 50°F (10°C).

Thursday: Mostly cloudy. High 63°F (17°C).