The forecast? Overcast, with a chance of shopping. Researchers are increasingly seeing a connection between weather and how consumers respond to their sales pitches. Negative advertisements elicit more successful responses when it’s gloomy outside, but when the sun’s out, the target audience craves positive reinforcement. One study, which looked at mobile advertising responses among 6 million users in China, saw remarkably strong weather correlations. Campbell’s Soup, for example, has taken to using storm names in its online blurbs, while other global brands are flocking to the Weather Channel, auguring a highly mercurial marketing climate.