The Tipping Point

Sunshine makes us nicer, inducing us to want to help others. On sunny days, regardless of the temperature, we answer more survey questions from people with clipboards and tip more generously. In dark Atlantic City hotel rooms, people give higher tips if the bellhop tells them it's sunny outside than they do if he tells them it's cloudy. Nice days put us in a good mood, which engenders helping and generosity, explains David Strohmetz, a psychologist at Monmouth University. "When we're in a good mood, we want to maintain that mood."

The Wisdom of Clouds

The weather even affects college applications, helping determine which types of applicants are admitted. Applicants who are strong academically are more likely to be admitted on cloudy days, whereas candidates who are strong socially are more likely to be admitted on sunny ones. Cloudy days call to mind thoughts of staying inside to read or study, explains Uri Simonsohn, the behavioral economist at the University of California at San Diego who conducted the study. A previous study found that cloudy forecasts prime people to think about academics.