"I think this popular belief — which I share to some extent, despite my own work in this area — represents what psychologists call a confirmation bias," David Watson explains in an email. He's the Andrew J. McKenna Family Professor of Psychology at the University of Notre Dame and author of the 2000 book "Mood and Temperament," which describes his own research on rainfall and mood.
"For example, if I am feeling down and look outside and see it raining, I may conclude that I am feeling gloomy because it is raining," Watson says. "However, if I am feeling down and look outside and see bright sunshine, I quickly conclude that it has nothing to do with the weather. So, we tend to notice and remember those events that are consistent with our beliefs and expectations."
In one study, for example, Watson and a colleague followed 18 Japanese college students over a three-month period in 1980, assessing their daily moods and correlating the ratings with weather summaries. To the researchers' surprise, their analyses of the data all demonstrated that the students' mood was unrelated to the weather. Watson subsequently gathered data from 478 college students in Texas during various periods during the mid-to-late 1980s and early 1990s, which he again compared to weather records. The result essentially was the same. Even on days when it rained an inch (25.4 millimeters) or more and there was no more than 10 percent possible sunshine, there seemed to be no significant effect on mood.
"My research tried to tease apart various potential factors, such as the presence versus absence of rain and daylight versus cloudiness (these variables are confounded, as it rarely rains when the sky is sunny)," Watson says. "I really could not find much evidence that anything influenced people's mood. When I started this research, I was very concerned about being able to locate the source of any effects. For instance, if people feel blue on a rainy day, it could be the precipitation, or the cloudiness, or the barometric pressure, or the fact that the rain restricts their activities and/or makes them more stressful/less pleasant. However, I really found no evidence that people felt sad on rainy days, so none of these variables seems to be crucially important."
Other studies seem consistent with Watson's findings that weather isn't that potent of an influence on mood, though two studies suggest that rain may have some effect on a minority of individuals. A study by Bulgarian researchers, published in 2011 in Advances in Science & Research, found a negative effect on emotion when the skies suddenly abruptly changed to cloudy, but the impact varied. Emotionally stable people were more resistant to the influence of weather changes, while those who were emotionally unstable were more strongly dependent upon them.
Another study of 497 Dutch adolescents and their mothers, also published in 2011 in the journal Emotion, found that 47.8 percent of the subjects were unaffected by the weather, and that 16.8 percent were summer lovers who reacted positively to warm sunny weather, while 26.8 percent were summer haters and 8.7 percent were rain haters, who were measurably angrier and less happy on days with more precipitation. On sunny days, in contrast, the rain haters were happier and less angry, though still fearful.
"The group [of] rain haters was pretty small, but the summer lovers didn't like the rain, either," lead author Theo Klimstra, an associate professor in the Department of Developmental Psychology at Tilberg University in the Netherlands, says in an email. "So, the total group of people who didn't like the rain was about 25 percent of the sample. The main difference between the rain haters and summer lovers was that rain haters didn't react as strongly to a lack of sun and low temperatures as summer lovers did, whereas summer lovers didn't react as strongly to the rain as the rain haters did."
Klimstra said it was surprising that about 75 percent of the subjects weren't negatively affected by the rain. "We examined whether the Big Five traits [openness, conscientiousness, extraversion, agreeableness and neuroticism] were related to our weather types, but that wasn't the case," he explains.
"The most likely explanation is that people are just less bothered by rain than we like to believe," Klimstra says.