Even as East Bay MUD proposes its first water-rationing measure in two decades, this week temperatures are expected to soar toward the century mark.
For your garden, this means get a head start (i.e., now) on keeping your plants hydrated. If you're irrigating with a spray system, see whether your controller can be programmed to repeat cycles — so that rather than watering once for ten minutes, which may deliver more water than the soil can absorb at once — your system waters each zone once for five minutes, then repeats the cycle for another five — so Zone A is absorbing while Zone B is receiving. If you're not sure how much water your plants should be getting, get to know your local Master Gardener; you can also extrapolate some good information from publications developed for commercial growers.
If you're irrigating with a low-flow (drip) system, you will want to increase the length of each cycle and/or add a "syringe" cycle in the middle of the day, effectively giving the plants a drink when their transpiration rates are highest.
You'll also want to make sure all that precious water stays in the soil, where the plants can actually get it, rather than evaporating into thin air. The most effective way to do this is with a generous layer of mulch. Most often we think of mulch as fir bark, which is ground to various consistencies (or shredded into "gorilla hair").
However, there's more than one way to mulch: compost is wonderful, adding nutrients to the soil even as it holds water in; and even pea gravel is effective (although pricey and doesn't decompose like organic matter). Some municipalities even give away free compost to residents. The key with mulch is to apply it generously (I prefer a depth of least 3 inches) and regularly. Remember, organic matter like bark and compost break down over time; so plan to reapply an inch or so at least a couple of times a year.
There are plenty of other considerations in creating "water-wise" gardens. The California Water Service has some good resources, including a list of drought-resistant plants; if you've got good tips for getting your garden through the heat, please let me know!