@myshkin_ Exactly my thought. The song refrain is repeating in my brain, "winter, spring, summer or fall... all you have to do is call..."
Or as in, "When summer comes, we'll be swimming in the ocean" whether summer is tommorrow or 6 months from now.
There is a song, "in the summertime" but that's not summer.
There's the famous, "in the winter of our discontent" where the specific season is modified, so we know it's a specific winter. So I'll suggest the definite article is included when a specific season is being referenced, as in "the spring of the Covid crisis." :-( So, I'm with myshkin_ . "The definite article is less frequently implemented when using the word for any particular season. So it's interesting.
But then again (sorry for the dissertation) seasons are super important in Sweden, so perhaps that's the reason: the language acknowledges this.