Yes, this UK weather is a charmer for certain. Taking some temperature readings in several pots today, I noted that just inside the pot near the edge was as near as darn it 48 C. So said my probe.
Thought I would mention or remind peeps that this direct sun heat on a shallow pot can be as devastating as a really cold winter. Actually, to be fair you have more chance of winning the battle with a hard winter than you do with heat. In the sun this afternoon it was here on my patio a smidgen under 50C in direct sun, and 28C in the shade.
Any Bonsai that is ready for a repot, or has roots close to pot edge is hugely vunerable in this hot weather. Whilst sun for many species is a huge bonus for the foliage, it is most certainly NOT for the roots.
Like winter in the wild; to some extent the roots can escape the horrendous cold. In Summer they can do similar. In a pot it is entirely different, and one must think about tree / pot management. Be warned, it can kill much quicker that a cold spell!
When watering tree pots; do your best to let the water in the can sit and warm up a touch. Cold water on warmed roots can be hugely detrimental. Think how it felt when you jumped in the river that time for a cool off!