In general during hot summer months, you should be watering your lawn up to three times per week if there wasn't any recent rainfall. As a general rule of thumb, watering up to one inch deep each time you water your lawn is ideal.
WATERING SCHEDULE
Deep watering helps to encourage deep root growth. Deeper roots stay cooler and stronger to better protect your lawn and garden from heat stress. Allow a deep watering at least once per week, twice if the temperature exceeds 100 degrees or more for several days in a row.
Watering on a hot summer afternoon is a horrible idea. The liquid will evaporate too quickly and may not reach your grass's roots, so heat and irrigation shouldn't go together. Instead, the best time to water grass during summer is in the morning. The ideal time for morning watering is before 9 AM.
To correctly water your lawn look at a thermometer outside. If it's 70-80 degrees outside try watering 2-3 times a week. During the spring your lawn will be fairly easy to manage so you don't have to water all the time. In the blazing summer, when temperatures are between 90-100+, try watering 3-4 times a week.
During really hot weather, water your vegetables at least two to three times a week. Watering the garden deeply is critical. The water must go down, down, down to encourage deep roots and get away from the hot soil surface.
In times of extreme heat, it is vital to water your lawn for about 30 to 45 minutes daily. Once the temperatures drop below ninety, you can cut back to watering three to four times a week, until that blissful thunderstorm comes and quenches your lawn's thirst!
The best time to water your garden in summer is from 6 am to 10 am—before the heat of the day sets in, giving your plants plenty of time to drink up and any moisture on the leaves to dry off before nightfall. What is this? If watering in the morning isn't possible, the next best time is from 4 pm to 7 pm.
It is ideal to water lawns about one inch of water per week. To determine how long you need to water to get one inch, place a plastic container in your yard and set a timer. On average, it will take 30 minutes to get a half inch of water. So, 20 minutes, three times per week will give a lawn about an inch of water.
Typically, most lawn irrigation periods during the summer should last between 25–30 minutes each. This amount of time depends on a lot of different factors though. As previously stated, each irrigation system or sprinkler can deliver different amounts of water and it's important to hit that 1 inch per week requirement.
Once temperatures reach 77 degrees, it becomes too hot for root growth, and root growth ceases. When temperatures reach 90 degrees, it becomes too hot for shoot growth and the grasses stop growing and begin to fall dormant, with the surface grass turning a brown hue.
Use a soaker hose
This is probably the best thing to do for water conservation in the extreme heat! When it is 100+ degrees and it hasn't rained for months, it can be hard to keep the lawn alive without a really high water bill. If you are on water restrictions, you don't have an option anyways.
Grass needs the benefit of the day to dry and heal before dusk settles. Since mowing your grass in the early morning can damage it and mowing it during the early afternoon can burn it because of all the high temperatures, the ideal time is mid-morning. That is of course if you're free during that time of day.
It is ideal for watering your lawn about 1 inch of water for every single application per week. On average, it takes 30 minutes to disperse 0.5 inches of water. Therefore, you must water your lawn in hot weather three times per week, for about 30 minutes each, to get an inch of water on your lawn.
1) Watering for Too Long
This should be no more than three times per week. Set a timer for 20 minutes and stick to your schedule, even if you think the lawn needs more water. You don't want to oversoak it.
Most grass needs watering between 20 to 40 minutes at a time. Water your grass one to three times a week in peak growing seasons. Your grass type, region, and amount of rainfall impact watering times. Watch out for signs of too much or too little watering to avoid disease or dead grass.
Most lawns need to be watered no more than three days a week in the spring as well as in the summer and two days a week in the fall. This watering schedule is recommended under normal water supply conditions.
If your sprinkler output is 1½ inches per week, your sprinklers should run for only ⅓ hour or 20 minutes that week (½ divided by 1½). On a twice-weekly watering schedule, run your sprinklers 10 minutes each time.
Sprinklers generally cover up wider ground and spread out water at a slow yet steady pace, which makes all the soil moisturized evenly and soaked underground. A watering hose takes time to cover space and can clutter the soil if there's too much water.
The answer is that it usually takes up to 30 minutes to get a half inch of water. Watering 3 times per week equals to an inch of water on a lawn. Plants can be watered 1 to 2 times a week in seasons where there is a higher chance of rainfall and less evaporation.
If done correctly, you can water late afternoon, when the heat is wearing off, and have the lawn dry out before night time. I would say starting around 3-5pm and ending no later than 7pm. Even then, you may be setting your lawn up for fungus and disease. If you have an automated system, set it up for the early morning!
The best time to water outdoor plants is in the morning when temperatures are usually cooler. This gives the plants time to absorb the water so they can get through a long, hot day. The second-best time is late in the afternoon or early in the evening. Try not to water at night.
Pros of watering a lawn at night
'It can help to prevent evaporation, which means that more water will reach the roots of the grass. Plus, it also helps to cool down the lawn in hot climates. 'There's also a chance that it can reduce noise pollution, as there are fewer people awake to hear the sprinklers running. '