While most of the south is used to hot and dry for days on end, other parts of the country aren't. I'm not here to argue about using sprinklers and whether it's a waste or not - if you're not on water rationing, and you're the one paying the bill, it is your choice after all! However, I've noticed that those in areas not used to the crispy grass don't realize that using a sprinkler mid-day is simply wasting money. If you want to use the sprinkler, the best time of day is after dusk - about 9 PM these days - or very early in the AM, around 5. Any other time of day, the majority of the water will simply evaporate before it gets deep enough into the ground to help your lawn.
And don't forget to set a timer, if you don't have your sprinkler set to go on and off automatically! Even crispy, there's only so much water the ground can absorb. Save yourself some money!
Regardless of whether you are watering your lawn or not, have your garden hose ready to go in case of a spark. The dry grass can burn very quickly, and you don't want to see your house catch on fire before you can get the hose hooked up!