My 'lawn' is a mixture of pasture grasses, clover, buttercups, daisies, and dandelions. I don't have an irrigation system, but have found myself watering it in Aug-Sep more often lately. So far this year, we are mowing much more frequently. You may find it beneficial to fertilize in fall and spring with an organic product to give your grasses the upper hand (healthy grass will often choke out lawn weeds). My folks lived in Seattle and their lawn turned almost totally brown every summer (they had much more impermeable surface than I do) but it always recovered. Much depends on your tolerance level. Mine is pretty high.
