If the trees are higher than the lightning rods, there is a high probability of lightning striking the trees.
In a few places, I have been; I have seen how lightning strike a tree. And near to this tree, lightning took a chunk out of the side brick.. as it tries to find it's way to the earth.
The danger of lightning is that one will never hear it coming. As by the time it does strike... the sound of it will come too late.
Thus, if there is any sign of potential rain, best to keep clear of the sky garden! Pronto!
If one should be caught in a thunderstorm... the safest is to go into that trellis area. As it's roof would have lightning rods that have metal trailing towards the ground....