As the summer months begin to give way to autumn, the stoic Ukrainian soldiers are fighting through the heavily defended Russian lines across the south of their country, as multiple breaches across the most heavily defended lines have been widely reported.
"The summer months" means "June, July, and August".
June already gave way to July, and July did to August, and August did to September.
Moreover, calendar months don't 'give way' to their successors and they abruptly end at midnight on their last day.
Therefore, I think that "months" is not natural or idiomatic.
What do you think about that?