FORECAST ACCURACY REPORT
Air quality conditions in December 2018 were in the Good Air Quality Index (AQI) category on 10 days, Moderate on 19 days, and Unhealthy for Sensitive Groups (USG) on 2 days. Air quality conditions in December 2018 were slightly better than in 2017 and similar to conditions observed in 2016.
All four of the highest AQI days in December were due to PM2.5. On these high AQI days, calm to light southerly winds limited pollutant dispersion and transported pollutants from Mexicali into the Imperial Valley.
There were also several strong low pressure systems that passed through the Imperial Valley in December. These strong low pressure systems are often accompanied by gusty westerly winds in the Imperial Valley; however, precipitation associated with these systems generally kept dust from being lofted into the air, which limited PM10 levels.
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