Skip to Content
Biotechnology and health

Warmer weather could slow the spread of coronavirus—but not by much

Several initial analyses of transmission data suggest the pandemic could ease up in summer. But that doesn’t reduce the need for measures like social distancing.
March 19, 2020
People walk on the street in Macau wearing face masks to protect themselves from coronavirus.
People walk on the street in Macau wearing face masks to protect themselves from coronavirus.Macau Photo Agency / Unsplash

The news: Higher temperatures and humidity are correlated with a lower rate of the novel coronavirus’s spread, according to early research that has yet to be peer reviewed. The hypothesis is plausible: the climate’s impact on the influenza virus is well established, for example, and a similar phenomenon has been suspected for the SARS coronavirus as well.

The results: In the most recent analysis, which used data compiled by Johns Hopkins University, two MIT post-docs in the civil engineering and cognitive science departments found that the maximum number of coronavirus transmissions has occurred in regions that had temperatures between 3 and 13 °C during the outbreak. In contrast, countries with mean temperatures above 18 °C have seen fewer than 5% of total cases. This pattern also shows up within the US, where southern states like Texas, Florida, and Arizona have seen a slower growth rate than northern states like Washington, New York, and Colorado. California, which spans north and south, has a growth rate that falls in between.

Other evidence: Two other preprint papers have drawn similar conclusions. The first, posted on Monday by two researchers from Spain and Finland, found that 95% of positive cases globally have thus far occurred at temperatures between -2 and 10 °C, which closely tracks with the MIT results, and in dry conditions. The second, posted earlier this month by a team led by researchers from Beihang University in China, also looked specifically at transmission rates across Chinese cities. It found that in the early days of the outbreak, before any government interventions, hot and humid cities saw a slower rate of spread than cold and dry ones.

Correlation, not causation: None of these papers have been peer-reviewed, and the correlations could be due to confounding variables. Every country has responded to the pandemic with different measures, for example, which could also affect differences in transmission rates. While the Chinese researchers tried to control for this by looking at data from the early days of the outbreak, the other papers did not.

Does this change anything? Other factors like population density, quality of medical care, and government responses also affect transmission—perhaps more than weather does. In a recent post, Marc Lipsitch, the director of the Center for Communicable Disease Dynamics at the Harvard School of Public Health, echoed this analysis. “While we may expect modest declines in the contagiousness of SARS-CoV-2 in warmer, wetter weather,” he wrote, “it is not reasonable to expect these declines alone to slow transmission enough to make a big dent.”

This means that for the Northern Hemisphere, the path forward shouldn’t really change: governments should continue to do what they can to reduce circulation of people, and individuals should continue to practice social distancing to flatten the outbreak curve. The good news is that if climate constraints do kick in, nature will also be in our favor.

Update: The story was updated to clarify the fact that the MIT researchers are not epidemiologists. The headline has also been changed to more accurately reflect the conclusion of the story.

Deep Dive

Biotechnology and health

This baby with a head camera helped teach an AI how kids learn language

A neural network trained on the experiences of a single young child managed to learn one of the core components of language: how to match words to the objects they represent.

An AI-driven “factory of drugs” claims to have hit a big milestone

Insilico is part of a wave of companies betting on AI as the "next amazing revolution" in biology

How scientists traced a mysterious covid case back to six toilets

When wastewater surveillance turns into a hunt for a single infected individual, the ethics get tricky.

The next generation of mRNA vaccines is on its way

Adding a photocopier gene to mRNA vaccines could make them last longer and curb side effects.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.