Sunny with 30% chance of food poisoning: How weather influences salmonella
There may be a way to forecast your risk for salmonella exposure and food poisoning in the future, and it has to do with your weather forecast
Every year, countless food products are recalled from grocery stores in Canada due to possible salmonella contamination.
Salmonella is a bacteria known to cause food poisoning in humans—causing symptoms such as vomiting, diarrhea, severe dehydration, and, in extreme cases, death.
Recently, scientists have found a link between salmonellosis (food poisoning through infection of salmonella bacteria) and the weather.
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In a paper published in the Journal of Infection on Jan. 15, 2025, scientists used 17 years worth of data from several diagnostic laboratories throughout England and Wales and compared salmonellosis cases against local weather factors at play on the day of each case. A computer model was then used to simulate a timeline of salmonellosis cases based on population and weather conditions.
"[Left] Time-series of modelled and laboratory-confirmed reported cases of salmonellosis across England and Wales at daily resolution. [Right] Seasonal patterns for daily salmonellosis cases averaged over the entire study period. Weather factors analyzed: mean air temperature, relative humidity, and day length." (Gonzalez-Villeta et al., 2025) CC BY 4.0
The modelled pattern showed there is, in fact, a relationship between cases of food poisoning from salmonella bacteria and certain meteorological factors.
Average air temperature and day length seemed to have the greatest influence on food poisoning risks, with modelled cases increasing for temperatures above 10°C on days with 12-15 hours of daylight—in other words, summer days.
These links could all be contributed to the fact that people tend to spend more time outdoors during warm summer days and participate in activities such as swimming in communal pools and eating outside.
Warm temperatures are also known to promote bacterial growth, with salmonella bacteria being no exception.
Other, less influential factors that the scientists noted to contribute to increased instances of food poisoning include relative humidity, rainfall, and increased dew points.
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While there are plenty of non-meteorological factors that go into the risk of salmonella exposure, such as livestock proximity to crops and water sources, the results from this study suggest there is indeed a connection between salmonella and the weather—especially temperature.
As weather forecasting continues to improve, it’s possible that food and agricultural agencies could become more aware of when and where salmonella contamination is likely to occur and take steps to prevent it.
But in a world where average global temperatures continue to rise and extreme weather events promote the spread of disease, we will likely see more cases of salmonella exposure. So make sure to keep an eye on food recalls because you could be at greater risk of this unpleasant illness in the future.
Header image: Getty Images/Ralf Liebhold