For the months of July and August (in Northern and Central Utah), the Utah Division of Water Resources (DWR) recommends watering for 21 minutes every 3 days.
Here is some information from the Utah DWR website.
Monthly Lawn Watering Guide
A typical Utah lawn has a water demand curve that begins in mid-April, rises to a peak in July, and then falls rapidly until mid-October. Adjusting your timer monthly to better follow this demand curve will save you water and money. An easy way to do this is keep the minutes constant and increase or decrease the number of days between waterings as shown below.
How do I water plants other than grass?
If your lawn and decorative plants are watered by different sprinkler zones, you will be able to save even more water. Shrubs, flowers and other decorative plants require 25-50% less water than the lawn. If possible, water these zones a few minutes longer than the lawn but half as frequently.
What if I already water less than recommended?
The recommendations are based on average conditions. If you already water less and are satisfied with how your lawn looks, don't increase your watering time. Instead, try decreasing the time! Turn down the minutes until you begin to see stress in your lawn, then turn it back up a bit and leave it. As you fine-tune your schedule, you will save even more water and money than this schedule suggests!
What if the recommended times are not enough?
If this schedule does not seem to be enough water for your lawn, please check your system for inefficiencies and maintenance issues before increasing your run times. Watering the whole lawn to green-up just a few brown spots is an inefficient use of water.