I recently visited the home of a master gardener friend, and her lilac was blooming. I was amazed, but she acted like it was no big deal and said it was because we'd had cool temperatures followed by an unusual warm spell. She said it had fooled the plant into thinking winter was
over. Sorry now I didn't ask her if that would have an effect in spring. At the very least, maybe it helps to know your shrub isn't the only one doing that!
'Mare

My plant is in 18inch container. My neighbors who have their lilac in ground their plant does not show any sign of growth at tips. They are just sticts with brown leaves. I am wondering whether the buds will bloom or not because by next week the temperatures are going down into low 40's. How this will have affect for spring bloom is something i need to know.

Lilacs do form their buds in the fall. You'd think the buds would die when they get frozen, but they don't.

If the plant actually blooms during the fall, my guess is that it won't bloom the following spring, but I don't know that for sure.

Good luck with it!

Jennifer