The heat can quite a toll on lawns in the summer. Lack of rain and warmer temperatures at night will cause turf to struggle. For those that do not have an irrigation system, here is a list of a few things that may help.
Mow taller (and less often) - Cutting less frequently = less stress on the grass. Longer leaf blades on the grass will allow it to store more water.
Mulch ( don't bag) when you cut - Grass has a high water content & leaving clipping on the lawn allows the grass to reabsorb this water and other nutrients. Clippings also help a little with insulating the roots of the grass plant from the heat & evaporation doe not happen as quickly.
Sharpen blades on mower - sharp blades cut grass evenly & allow a lawn to look good at a taller height. Dull blades tear grass unevenly and cause additional stress to the grass. Cutting with dull blades will cause a lawn to turn brown & go dormant quicker in drought like conditions - if the tips of the grass plant turn brown a day or two after mowing, it is probably time to sharpen the blades.
Less fertilizer - for lawn turf, less nitrogen = less growing and that means less water is needed. If the lawn is already mostly brown (dormant), you may just be feeding the weeds that sprout this time of year. There is an exception - if you are expecting a large amount of rain within a day or two then it is a good idea to apply a small amount of fertilizer (maybe 1/4 of a regular application) before it happens. Do this only if you know for sure that it is going to rain.
When to mow - Cooler times of day - early morning or late evening are the best times to mow. Mowing in the heat of the day may cause problems - the heat and the pressure from the mower tires may cause the grass to go dormant in strips. Avoid traffic on the turf as much as possible.
When it is hot and dry (with the exception of watering), less is often more. The best course of action is to simply leave the lawn alone. However , there are many thing you can do in the fall (which may include aerating overseeding or dethatching ) to better prepare you lawn for the next season.