This First Report of the WMO Research Board COVID-19 Task Team, provides an assessment of the state of knowledge of meteorological and air quality (MAQ) factors influencing the first year of the COVID-19 pandemic. The report critically appraises peer reviewed studies on the role of MAQ factors (Temperature, Humidity, Solar radiation, Air Quality, etc.) on the spatial and temporal variability of COVID-19 incidence and severity across climate zones, including clear interrogation of uncertainties. It also assesses the role of changing seasons on the trajectory of the pandemic at a range of time and space scales; and identifies appropriate methods, data and operational issues which can improve good practices in research and climate and environmental services.