Seasonal Sadness, Seasonal Euphoria

The blue feeling experienced by both SAD and SSAD sufferers can usually be dampened or extinguished by exercise and increased outdoor activity, particularly on sunny days, resulting in increased solar exposure.[25] Connections between human mood, as well as energy levels, and the seasons are well documented, even in healthy individuals.[26]

Physical exercise has shown to be an effective form of depression therapy, particularly when in addition to another form of treatment for SAD.[51] One particular study noted marked effectiveness for treatment of depressive symptoms when combining regular exercise with bright light therapy.[52]

https://en.wikipedia.org/wiki/Seasonal_affective_disorder