COVID-19 is killing African Americans at a rate 7% to 193% higher than the general population. Understanding why, as well as the reasons behind the wide variation, is paramount to saving lives. Here, we test two potential explanations for this effect. On the one hand, African Americans might be dying more because they have a lower average income (‘the Socioeconomic Hypothesis’). On the other hand, they might be dying more because their skin is more resistant to UV radiation, as we previously showed that COVID-19 infections and deaths decrease with higher irradiance (‘the Irradiance Hypothesis’). The two hypotheses are not mutually exclusive. We show that the overrepresentation of African Americans among COVID-19 deaths shows a significant negative correlation with mean solar irradiance, with a 20% decrease in Global Horizontal Irradiance leading to a 76% increase in the overrepresentation of African Americans amongst COVID-19 deaths. We then show that in Michigan, one of the US states with the lowest irradiance in early April, the % of each county’s population that is black, more than its median income, median age or % of the population above 65 years old, predicts COVID-19 morbidity and mortality rates. These results suggest a susceptibility linked to low irradiance may play a large role in African American vulnerability to COVID-19, and that black populations in (darker) locations with lower irradiance may benefit from sunlight exposure during the COVID-19 pandemic.