The Institute will get its first real dose of chilly fall weather this weekend as an Arctic air mass ushers in some of the coldest temperatures this area has seen in months. The frigid air will begin to make its intrusion after the passage of a cold front tomorrow afternoon. The frontal passage will be accompanied by a shift in the wind from southwesterly to westerly, and an increase in wind speed. After the front moves out, a mass of anomalously cold air will make its way down from Canada through New England over the course of the weekend. The result will be that by Sunday, low temperatures will be below 40°F (4°C) and the high may not even reach 50°F (10°C). The last times that low and high temperatures that cold were recorded in Boston were May 2 and June 2, respectively. By Sunday night, temperatures could even threaten to break the freezing mark for the first time since April 2. The predicted temperatures are also particularly low compared to the normal high and low of 61°F (16°C) and 46°F (8°C) for this time of year. It will likely take until Tuesday of next week to return to warmer, more seasonable temperatures.