Confused lilac

It's August and a week after the 100+ degree weather. My Korean Lilac has decided that it is time to bloom (it usually blooms in May.)

I am not sure why this has happened. I did prune the bush excessively after the spring bloom because it was growing way out of bounds. Did the heat trigger something? Or the long dry spell?

Spring photo of the same lilac bush.

Working at a gardent center/nursery I have also notice this happening to the lilacs. Specifically the Sugar Plum Fairy variety of lilac. It was only that kind and it was all of them, as we carry several lilacs. It was unusally and we got to enjoy the second bloom. As for the reason why, we have not found one yet. It could have been from heat stress.