I most certainty wouldn't, too hot and dry you'd not kèep them hydrated......hydrangeas struggle enough in dry weather when well established, let alone in this weather,
spring & autumn with anything pot grown and november to march for most things is my advice

if they are already bought and in pots then they would be better in the ground, but you will have to give them plenty [2-3 watering cans] of water for several weeks. Unless it rains heavily and persistently for several days.

Thankyou for your advice I am going to get more plants haven't got yet ...I have bought bushes awhile ago and put in ground before this hot weather and so far they are OK I hope ...

As you haven't bought them yet it is much better to wait until the autumn, and if you can,buy your roses bare rooted then - they are much cheaper than the potted ones and will establish well. Let the garden centre do the caring over the summer!

Thankyou all for your answers very helpful as always ..Sharon..:-) :-)