On days with high pressure—the clear, sunny ones—people who spent more than 30 minutes outside saw an increase in memory, mood, and flexible thinking styles. Those who spent the time indoors, though, saw a decrease. In a second experiment, the researchers asked 121 subjects to either spend time inside or outside on a warm, clear day. “Among participants who spent more than 30 minutes outside,” they reported, “higher temperature and pressure were associated with higher moods, but among those who spent 30 minutes or less outside, this relationship was reversed.” The participants who spent more time outside during the spring, but not during other seasons, had better moods.
“Temperature changes toward cooler weather in the fall did not predict higher mood,” they wrote. “Rather, there appears to be something uniquely uplifting about warm days in the spring.”
In summary, across the studies, spending more time outside on clear, sunny days, particularly in the spring, was found to increase mood, memory, and openness to new ideas. People who spent their time indoors, though, had the opposite effect, and “one possible explanation for this result is that people consciously resent being cooped up indoors when the weather is pleasant in the spring.”
People in industrialized nations spend 93 percent of their time inside, but the authors suggest that “if you wish to reap the psychological benefits of good springtime weather, go outside.”