What is spring fatigue?

Can the sauna help against spring fatigue?

Why do we feel so sluggish in spring, even though the sun is shining, the flowers and trees are in full bloom, and a warm breeze is blowing? For many people, springtime fatigue makes little sense; after all, the mood should be good when the sun is shining. For some people, however, springtime fatigue is a real problem that can manifest itself in low mood, exhaustion, irritability and even despair.