Inspect hoses and fittings. Watering is critical this time of year, and prolonged heat and UV exposure can weaken hoses, especially dark-colored ones, causing leaks. More common, though, are leaky joints, where washers are faulty or missing; replace them and make sure you tighten the connections. Smaller leaks can be strategically located to drip on specific plants, but big gushers, or lots of small ones, for that matter, will waste water, cause mud, and run up your water bill. When replacing hoses, remember: Heavier hoses may last longer , but they are HEAVY. So start out with the heavy stuff close to the spigot, and cover it with mulch to keep out the sun. Then think about lighter weight or even the little collapsible ones to drag along behind you.
Invest in a pop-up tarp. They're on sale right now! No gardener should be without one. They pop up easily and make you able to garden in all weathers. Move them as needed to keep the sun off your work, or to keep rain from drowning you while you plant. Practice putting it up and down a few times before you actually take it out into the yard, and be sure to weight it down if you're trying to work in heavy winds. Come to think of it, stay the heck in the house if the winds are heavy, because trees could fall on you.
Check out the half-price shrubs. While we're speaking about sales, nurseries are unloading their shrubs and trees at half-price because they don't want to have to take care of them all summer long. Be sure to ask about limited warranties, guarantees, or return policies as these may be different because of the sale prices.