COVID19 is a seasonal climate-driven disease across both hemispheres

The role of climate in the population dynamics of COVID-19 remains poorly understood, and a true seasonal signature has remained elusive. Data from both hemispheres and the second wave provide opportunities to further examine climatic drivers. With a statistical method designed to detect transitory associations, we show consistent negative effects of temperature and absolute humidity at large spatial scales. At finer spatial resolutions we substantiate these connections during the seasonal rise and fall of COVID-19. Strong disease responses are identified between 12-18°C for Temperature and 4-12 g/m3 for Absolute Humidity. These results classify COVID-19 as a seasonal low-temperature infection, and point to the airborne pathway as an important contribution to transmission for SARS-CoV-2, with implications for control measures we discuss. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement AF acknowledges the financial support of HELICAL as part of the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No.81354. XR acknowledges support from the Spanish Ministry of Science and Innovation through the Centro de Excelencia Severo Ochoa 2019 2023 Program (CEX2018 000806S) and support from the Generalitat de Catalunya through the CERCA Program. A.SJ. was supported by a fellowship from la Caixa Foundation, Spain (ID 100010434, fellowship code LCF/BQ/DR19/11740017). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The current study requires no ethics committee aproval. Data used are public fully anonymized records at an aggegate scale of regions in countries. All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data used is public and obtained from public repositories, as indicated in the manuscript