Abstract: www.nature.com/scientificreports OPEN Effects of climatic factors on COVID‑19 transmission in Ethiopia Fitsum Bekele Endeshaw1, Fentabil Getnet1, Awoke Misganaw Temesgen1, Alemnesh H. Mirkuzie1, Latera Tesfaye Olana1, Kefyalew Addis Alene2,4* & Solomon Kibret Birhanie3 Climatic conditions play a key role in the transmission and pathophysiology of respiratory tract infections, either directly or indirectly. However, their impact on the COVID-19 pandemic propagation is yet to be studied. This study aimed to evaluate the effects of climatic factors such as temperature, rainfall, relative humidity, sunshine duration, and wind speed on the number of daily COVID-19 cases in Addis Ababa, Ethiopia. Data on confirmed COVID-19 cases were obtained from the National Data Management Center at the Ethiopian Public Health Institute for the period 10th March 2020 to 31st October 2021. Data for climatic factors were obtained from the Ethiopia National Meteorology Agency. The correlation between daily confirmed COVID-19 cases and climatic factors was measured using the Spearman rank correlation test. The log-link negative binomial regression model was used to fit the effect of climatic factors on COVID-19 transmission, from lag 0 to lag 14 days. During the study period, a total of 245,101 COVID-19 cases were recorded in Addis Ababa, with a median of 337 new cases per day and a maximum of 1903 instances per day. A significant correlation between COVID-19 cases and humidity was observed with a 1% increase in relative humidity associated with a 1.1% [IRRs (95%CI) 0.989, 95% (0.97–0.99)] and 1.2% [IRRs (95%CI) 0.988, (0.97–0.99)] decrease in COVID-19 cases for 4 and 5 lag days prior to detection, respectively. The highest increase in the effect of wind speed and rainfall on COVID-19 was observed at 14 lag days prior to detection with IRRs of 1.85 (95%CI 1.26–2.74) and 1.078 (95%CI 1.04–1.12), respectively. The lowest IRR was 1.109 (95%CI 0.93–1.31) and 1.007 (95%CI 0.99–1.02) both in lag 0, respectively. The findings revealed that none of the climatic variables influenced the number of COVID-19 cases on the day of case detection (lag 0), and that daily average temperature and sunshine duration were not significantly linked with COVID-19 risk across the full lag period (p > 0.05). Climatic factors such as humidity, rainfall, and wind speed influence the transmission of COVID-19 in Addis Ababa, Ethiopia. COVID-19 cases have shown seasonal variations with the highest number of cases reported during the rainy season and the lowest number of cases reported during the dry season. These findings suggest the need to design strategies for the prevention and control of COVID-19 before the rainy seasons. Since Corona Virus Disease 2019 (COVID-19) was officially declared by the World Health Organization (WHO) on 11 March 2020 as a global pandemic, the number of deaths and daily confirmed new cases have increased in every corner of the world. The pandemic is a serious global public health crisis affecting the physical, mental, social, and economic well-being of human ­beings1–3. Following the first reported cases of COVID-19 in Wuhan, China in late December 2019, the virus has quickly spread across the w ­ orld4. As of 11 March 2022, there were more than 453 million confirmed COVID-19 cases and over 6 million associated deaths around the g­ lobe3. As of 11 March 2022, COVID-19 has infected 466,064 persons in Ethiopia, with over two-thirds of the COVID-19 patients..