This paper responds to a request for advice on the impact of winter on the spread of COVID-19, and has been prepared by the Rapid Research Information Forum. This rapid report synthesises the evidence base on this matter and has been informed by relevant experts and has been peer reviewed.

Main findings:

• Notwithstanding the recent emergence of SARS-CoV-2, research suggests there will be some influence of winter on spread and severity of the virus.
• Lower humidity and air temperature can increase the viability and virulence of the virus and therefore its infectivity.
• Physical distancing supported by effective public policy measures will have a greater impact on managing the spread of SARS-CoV-2 than seasonal climate.
• The concurrence of COVID-19 with other viruses during winter, such as influenza, will likely exacerbate demands on health services, especially for vulnerable people and communities.
• The onset of winter may further exacerbate the psychological effects of COVID-19, especially if quarantining measures are extended.