This depends mainly on the size and age of the tree. Regardless of how often a tree is watered, each water application should be enough to saturate an area as wide as the drip line of the tree to a soil depth of 2-3 feet minimum. As a tree matures, it needs a wider water area of coverage...especially palm trees.
A great rule of thumb is: "Thorough watering is the deep and thorough saturation of the entire root system, allowing it to dry between waterings"
Watering frequency can depend on a few variables: Age of tree, type of tree, soil conditions and current weather conditions. Loose sandy soil dries out faster so more frequent watering is required where as tight soils may require less frequent applications. Newer trees don't have established root structures and require more frequent watering than when mature. Long periods of extreme heat dry out the soil faster dictating an increase in water frequency. For advice on surviving in periods of extreme heat or cold, read up on our weather protection guide