The study, which will be released Wednesday, used computer models to examine nearly 1.1 million reviews of 840,000 restaurants over nearly a decade.

Online reviewers posted most often in July and August, researchers said, but those reviews were more likely to be negative. And regardless of season, if the weather was uncomfortable, all the worse for the chef. The most negative reviews were written when it was colder than 40 degrees or warmer than 100 degrees, or if it was raining or snowing.

The researchers, Saeideh Bakhshi, a doctoral student at the Georgia Institute of Technology; her husband, Partha Kanuparthy, who works for Yahoo Labs; and Eric Gilbert, an assistant professor at the university, said the weather’s seeming sway over reviews surprised them the most.