The first week of December will be reasonably warm, with a mix of sun and clouds and highs in the mid-40s°F. A low-pressure system is situated over the Atlantic Ocean, but most of the precipitation is expected to stay away from the New England coast. The precipitation, if any, will be in the form of rain instead of snow. Temperatures will be on par with historical averages for Boston at this time of year.
On the west coast, however, temperatures will be much colder than average in the next few days. A low-pressure system is moving down from the Pacific Northwest over the Central Plains, bringing up to a foot of snow to the Rocky Mountains. Behind this system, a mass of cold air will settle over the western U.S. for several days. In places like the San Francisco Bay area, this may cause record-breaking low temperatures approaching and even passing the freezing mark.