Northern China in the 2015 winter months of November and December has witnessed the most severe air pollution phenomena since the 2013 winter haze events occurred, which triggered the first ever Red Alert in the air pollution control history of Beijing, with an instantaneous PM<sub>2.5</sub> concentration over 1 mg m<sup>−3</sup>. Analysis and modeling results show that the worsening meteorology conditions are the main reason behind this unusual increase of air pollutant concentrations and the emission control measures taken during this period of time have contributed to mitigate the air pollution in the region. This work provides a scientific insight of the emission control measures vs. meteorology impacts for the period.