in full bloom right now; at its peak
A literary set phrase describing something that is at its most flourishing or glorious moment, often used for flowers, beauty, or a person's prime.
The cherry blossoms are in full bloom right now.
She is shining at the peak of her beauty.
A set phrase composed of 今 (now), を (object marker), 盛り (peak, prime), and と (quotative/adverbial particle), literally 'as if now is the peak'.