Objectives: Road fog can form suddenly which necessitates more caution by the researchers as well as drivers due to low vision and related morbidities and mortalities. This study aimed at determining the pattern of accidents in fog and the relationship between driver, road, and accident with injury level in Guilan, Iran from 2014 to 2018. Methods: This is a retrospective descriptive-analytical study that investigated all accidents that had occurred in Guilan from 2014 to 2018. All of the data were entered into STATA software. The time-series estimators were used as the multivariate regression model for the presence or absence of any relationship between variables.Results: In fog, the fatality rate of traffic accidents was significantly higher than other climatic conditions (IRR = 1.471). The likelihood of fatalities in fog decreased with age while it increased when drivers were female (p = 0.001). Most of the accidents in fog condition had occurred in December (p=0.000), February (p=0.001) and November (p=0.012). The number of related injuries at 2 AM (p = 0.032), 3 AM (p = 0.019), and 2 PM (p = 0.02) significantly reduced. Moreover, the rate of mortality at 2 AM (p = 0.005), 9 AM (p = 0.012), 11 AM (p = 0.004), 13 PM (p = 0.008) and 19 PM (p = 0.003) were significantly lower. The rate of injuries was significantly higher in Anzali (P = 0.042) and Rasht (P = 0.018), respectively.Conclusion: In the fog, the fatality rate was significantly higher than that of other conditions. The pattern of accidents in fog decreased with age and increased in accidents involving female drivers. Most of the fatal accidents had occurred in fog in November, January and February, respectively. Road accidents in Anzali and Rasht cities were more fatal.