There are several theories on how best to water your lawn. The best way is to have a sprinkler system installed and have it set for you on your behalf. Watering your lawn requires a bit of strategy. Unless the weather forecast calls for hot dry weather, watering in May is really unnecessary. The grass grows in spring weather more than an inch per day and the cooler temperatures conbined with rainy periods is plenty of water for a lawn.
People who do not have sprinkler systems installed (or the majority of us) should consider watering three times a week in the mornings. Give your lawns a good soaking for about 40 minutes each time. This is no point in watering more than three times. Grass roots that are watered too much remain on the surface as their nutrients are always close at hand. Roots that are watered less often will grow deeper into the soil in search of water and nutrients. Many of our clients will leave it to mother nature if they believe there is rain in the forecast. In many circumstances it doesn't rain in your area and the rain is insufficent. Please watch for that.
Around labour day in the Ottawa region, the temperatures begin to cool once again and scaling back the watering is probably a good idea. Many of our clients turn their sprinklers off by mid-September as the cooler temperatures and morning dew is plenty to keep the grass growing.