This is no doubt one of the hottest, driest summers I can remember. However, I remember a mid-70's summer spent in Center, Texas building and landscaping a shopping mall. As I reflect on that experience, "Boy was it hot and dry." But the 80% or more humidity was lovely. It is all relative to what you are used to.
I'm not a weather forecaster or statistician (I can't even spell it), but I can tell you that plants need moisture year-round. In our area it is usually dry during June, July and August. So how do we supply needed moisture to plants during the dry months? By supplementing the rainfall and keeping the moisture in the root zone.
Plan on making changes this fall and winter for your landscape plants. First, inventory the plants to see which ones require high, medium or low moisture. Plants with similar water requirements should be placed in the same bed.
It is less difficult for an irrigation system to deliver adequate water to each plant when their moisture needs are similar. For instance, junipers and begonias in the same irrigated bed would be difficult to keep alive for very long. Junipers do not require as much moisture as the begonias.
Mulching the area with bark to a depth of 3"-4" around the plants will conserve the moisture in the root zone. Be careful to prevent the mulch from stacking up on the stems of the plants. The bare soil temperature in the summer can exceed 120 degrees.
Mulched soil is usually 25 - 40 degrees lower. This temperature difference can be an added benefit to the roots during the summer. Mulch will keep in the moisture whether it falls from the sky or is supplied though irrigation.
When supplemental watering is needed, add it slowly and in large amounts. The water should not run off the area you are irrigating. This is wasting the water we should be delivering to other plants. When water run-off begins to occur, move to a new area or shorten the time that the water is delivered to this area. Then, return to this area for additional water. The object is to allow the moisture to fill the top 2 to 4 inches of soil.
This is the root zone, or soil from which the plant will receive its moisture. A slender probe such as a screwdriver will be helpful to determine if the soil is receiving adequate moisture. On the other hand, this root zone can be over filled during the rainy season. If excessive saturation of the root zone lasts too long, roots may die and decay.
Keep plants with similar moisture requirements together.
Water deep to keep the root zone moist.