When temperatures consistently hit 85 degrees F, I recommend an inch of water twice a week for each lawn zone. Typically a good irrigation system with correct pressure should accomplish an inch in about 30 minutes. Test this yourself by capturing irrigation water in a shallow container with an inch marked. Our soils cannot absorb that much water at once so break the amount of time into multiple start times with about an hour and half between. The best time to irrigate is between 3 a.m. and 10 a.m.
I would suggest watering the shrub zones for 5 minutes 3 days a week. If your system does not segregate beds and lawn zones, use the lawn time.
Trees need 10 gallons per diameter inch. Water slowly. I use 15 gallons buckets with 2 X 1/4 holes drilled in the bottom and fill the buckets and allow gravity to water your trees.
Rain is superior irrigation because of its pH. Don’t counter Mother Nature’s perfect fluid with a high pH effluent from our water districts that contains high levels of chlorine. Have your irrigation system checked by a competent irrigation contractor.