Excited by budding trees, puffy white clouds, and the return of sunshine? You’re not alone.

Spring is a powerful physical demonstration of renewal in nature because all living species are growing and thriving again.

It’s a chance for us to grow and thrive too, even if the weather does remain chilly for a few more weeks. Because we do feel better in the spring—and it’s not just a trick of our minds with the passing of the equinox or the flipping of the calendar from March to April. So why do many of us experience this upswing in mood and general health during the springtime?

Neuroscience has the answer.

It comes down to the chemistry of our brain and nervous system, and how what is happening outside affects what is happening inside—on a micro level. The environment and the subtle and not-so-subtle changes that signal spring trigger changes in our brain chemicals, influencing our mood and behavior.

Lots of sunlight: The increased daylight during the spring and summer months does make us happier, according to science. Our bodies react to sunlight, signaling the brain to make biochemical changes that improve our mood.

More sunlight tells our bodies to produce less melatonin, which regulates both sleep and mood. We feel more energetic because our bodies are telling us we no longer need to be in hibernation.

Additionally, the sunlight affects our serotonin levels, the happiness hormone. When serotonin levels are high, our mood improves. In the winter, the opposite happens—the brain removes more serotonin—which some scientists link to SAD.

Active lifestyle: Both our brighter mood and the attractiveness of the outdoors urge us to shake off the sluggish habits we’ve fallen into over the winter. When we exercise, our bodies create endorphins, which make us feel good—that’s where the mood boost comes from after a vigorous workout or a run. Even better, increased activity means a rise in our serotonin levels, which has a similar effect to endorphins but lasts much longer.

Time outdoors: While allergy sufferers may avoid outdoor activities during the spring, pollen isn’t the only thing in the air come March and April. Phytoncides, the source of the scent of fresh greenery and forests, defend plant life against disease—and play a similar role in our bodies, boosting immunity and fighting inflammation. Studies also show that time spent in nature can lower blood pressure and improve our health overall.

Social interaction: The colder weather and early darkness often drive us into hibernation mode, where we are reluctant to go out, often holing up in our houses and gluing ourselves to television or social media. With spring, though, come the community events that draw us back out and among other people—with more chances to interact and bond with others. Even a simple smile and hello to the neighbors on an evening walk can make us (and them!) feel good. Positive interactions and  human connections improve our mental health and our response to stress.

Improved focus: Our brain activity is cyclical as well, and scientists say that the amount of “work” our brains have to do to perform various tasks changes with the seasons. In the spring, we’re better able to focus for longer periods—which may result in greater productivity, and an associated uptick in positive mood.

While spring may not bring good news to everyone, for many it is a chance for growth and renewal right along with the trees and plants around us. How do you experience the change in seasons? What are your favorite aspects of spring? What activities do you enjoy? Share your own story in the comments.