California smoke cover graphic 2018-2021 (IMAGE) University of California - Davis Caption Maps from a UC Davis study show sites (colored dots) and the annual number of days with medium to high density smoke cover from 2018 to 2021, using a red color gradient. Credit UC Davis Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. No derivatives or adaptations of the work are permitted. License CC BY-NC-ND Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.