Season of Growth’s last ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.

If multiple creatures enter the battlefield under your control simultaneously, you’ll scry 1 for each of those creatures. You won’t look at more than one card from your library at once.

Season of Growth’s last ability triggers when you cast a spell that has multiple targets, as long as at least one of those targets is a creature you control. It doesn’t trigger multiple times if you cast a spell that targets a creature you control multiple times or that targets multiple creatures you control.