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Boston Weather: 83.0°F | Partly Cloudy

Weather: Hot, Cold, Hot, Cold

By Bill Ramstrom
STAFF METEOROLOGIST -- The wild swings in temperature over the last couple days may continue today, but starting tomorrow, more tranquil weather will prevail. The culprit for these drastic changes is the large temperature difference between the land and the ocean which is common in the spring. The temperature at Logan Airport dropped 32F (18C) in one hour late in the afternoon Wednesday -- from 91F to 59F, as the wind shifted from westerly to easterly.

While a large mass of warm air has been building over the middle of the country all week, water temperatures in Boston Harbor remain in the chilly upper 40s F. This large temperature contrast also implies that the density of the cool air over the ocean is much higher than that of the warm air over the land. In the absence of strong flow, the configuration of a vertical column of warm air next to a column of cold air is not stable. The cool air will tend to slump inland, while warm air moves offshore at higher levels.

A cold air mass from Canada will begin to move into the area on Saturday, putting an end to the hot weather that we have had. A few showers could form ahead of this on Friday night, but not much precipitation is expected. Sunday and Monday will also feature sunny skies, but cool temperatures.

Extended Forecast

Today: Breaking clouds, then sunny. High 72F (22C).

Tonight: A chance of a shower. Low near 50F (10C).

Saturday: Some sun. High 71F (22C).

Saturday Night: Much cooler and clearing. Low 43F (6C).

Sunday: Sunny but chilly. High 55F (12C).

Monday: Continued fair and cool.