Lilac Tree diseased or healthy?

Smidgedad

This year the east facing side of my lilac tree either died or the buds that did develop suddenly stopped and withered.  The other half if the tree is in performing well and new side shoots are developing.  Has anyone else experienced this?  I assume that the tree is not dead given new shoots are forming, but I would love to know the cause of this.  I’m going to cut away the affected areas. 

philippasmith2

Weather damage sounds likely.  It's been a topsy turvey year for gardens so far

Smidgedad

Thanks. There was certainly a great deal of frost in April and the side that is affected gets the morning sun. I’ll just cut away the dead parts and hope the gaps are filled soon.