BERLIN — Spring is finally here, and thanks to the sun’s warming rays, many people are now in very good moods. But while many believe the first warm days of the year simply feel good, spring euphoria is not an illusion — it can be scientifically explained.

We asked three researchers in different disciplines to describe the relationship between good weather and happy moods.

The psychologist. Human beings are programmed to rest when it’s dark, and to be active and in high spirits when it’s light, says Peter Walschburger, professor emeritus of biopsychology at the Freie Universität Berlin. “We react massively to light,” so conscious experience and human behavior change radically on fine spring days.

“Suddenly there are lots of people out and about, so you have a tendency to go outside,” he says. Of course, spring also means a different wardrobe that tends to show off our bodies more than winter duds, which stimulates attraction. “You see more couples out strolling,” he says. “There’s a general resonance effect.” Scents and bird song also influence us, Walschburger says. “So spring is an unbelievable time,” as opposed to winter, when we live a more confined existence, sleeping longer and putting on a little weight.

The endocrinologist. Sun rays change our hormonal balance. Hormones that have a particularly strong influence on our moods are the sleep hormone melatonin and the happiness hormone serotonin, explains Helmut Schatz, spokesman for the German Society of Endocrinology. When it gets light earlier and the sun shines more strongly, more light hits the eye. Thus the pineal gland — sometimes called the third eye — sends an order to the brain to lower melatonin production, “which makes us more lively.”

At the same time, serotonin increases in the body when it’s sunny, and with more of the happiness hormone in our blood, our moods improve. Warmth also impacts our moods, although the cold doesn’t necessarily contribute to worse moods. As Schatz points out, a cold winter’s day is not necessarily a downer. “You also feel pretty good sitting in front of a ski hut in the sun,” he says.

The doctor. People are sensitive to weather and always have been. “It’s in our genes, it’s ancient,” says medical meteorologist Gerhard Lux of the DWD weather service. Though our wellbeing in no longer weather-dependent — because of air-conditioning and heating — the weather still influences us.

In spring, both the sun’s rays and a seasonal rhythm are responsible for a spring in our steps. “Suddenly, we feel like going somewhere where we can get a cool beer or an ice cream,” Lux says. “The wish to be a part of things is activated.”

Certain effects of light lead the body to focus on particular desires such as food and sex. In principle, it’s a positive sign, when the body reacts positively to a beautiful day, he says. “It’s a sign that things are in good working order.”