On the September 11, 2022, a severe dust storm affected the northeastern and eastern provinces of Iran, as well as the southern shores of the Caspian Sea, so that the visibility in the two provinces of Gilan and Mazandaran was greatly reduced. The occurrence of such a dust phenomenon in the north of Iran, where events like this rarely happen, is unexpected. The purpose of this study is to investigate the causes of this phenomenon, identify active dust sources at the time of its occurrence, and investigate the ability of an operational dust model to forecast it. For this purpose, satellite data and products, ERA5 reanalysis data and DREAM8-MACC model output were used. The results showed that the activity of dust sources on the eastern shores of the Caspian Sea, southern Turkmenistan near the border of Iran, its central areas around the Kara-Kum desert, its northern and northeastern regions, as well as parts of the Amu Darya and Morghab rivers in eastern Turkmenistan caused such widespread dust storm. Based on synoptic analysis, the presence of a dynamic low-pressure system in Kazakhstan, a high-pressure system over the Caspian Sea and a thermal low-pressure center in the east of Iran in the border region with Afghanistan are among the atmospheric factors for the occurrence of this dust phenomenon. The evaluation of the model output also showed that the model underestimated the AOD values in forecasting this phenomenon and did not predict the dust transfer to the southern shores of the Caspian Sea.