YOUR TREES NEED WATER - JUST LIKE YOU!
Long slow watering for deep root is a best. Invest in a soaker hose. Vancouver allows for watering anytime by hand, or using soaker or drip irrigation for trees. Basically if the application is slow, the water is more readily used by the tree. Any water is better than no water. Use watering your trees as a way to cool yourself in the hot evenings, the simple act of watering cools the immediate area you are standing. Avoid watering close to the trunk, the absorption roots are mostly concentrated to the outer edge of the canopy or the drip line.