It depends on whether you have been pruning it to keep it in shape. Hydrangeas flower on old wood, the previous seasons growth. So if you have been trimming it back you will have stopped it flowering the following year. It's a bit of selective pruning for these, leave the flower heads on in cooler climates to protect the young buds below them.
See the following RHS site for details.
https://www.rhs.org.uk/advice/profile?PID=516

Otherwise it may be too hot, dry, young, another RHS page to check out.
https://www.rhs.org.uk/advice/profile?pid=122

Best of luck, I have cut mine back hard before reading the above and stopped them flowering!!