If you have not watered your trees you need to start today. Particularly if your tree was planted in the last year you need to be watering at least twice a week. If your trees are more established you still need to water at least once a week.
Simply pull out that hose, turn it up about half way and let it run over the root ball of the tree.
Also, make sure you have mulch around the tree to hold in the moisture, but DO NOT pile the mulch up on the tree trunk as this will actually smother the tree.
What a wonderful feeling; the rain stopped the sun came out and we were able to mow the entire tree farm and it looks great, so green!