Checking Google Ngrams, I was surprised by how common 'come [season]' is.
'Come spring' and 'come fall' vastly outnumber 'when ... comes'. 'Come
summer' and 'come autumn' outnumber the equivalent and 'when winter comes' is
slightly more common than 'come winter'. In each case 'come [season]' has
grown in use since about 1900, and 'when [season] comes' has dropped since
about 1940.
https://ell.stackexchange.com/questions/27371/come-autumn-meaning
Come fall, the plant dries out and dies.
https://youtu.be/dATZsuPdOnM?t=71
It's kind of a fixed expression: come + time/date/event:
It'll pick you up come morning [when morning comes]
Come the revolution [when the revolution happens] there will be no more banks
https://forum.wordreference.com/threads/come-morning.2246287/