Many gardeners stop planting lettuce after spring thinking it's just too hot for them to grow well.  NOT SO!  Change up your seeds, your location, and your soil block strategy and all's well with wonderful baby greens all summer long.  First, pick out a place in the hot sun for your 2" blocks to germinate.  Second, research some lettuce varieties that can tolerate heat or cold and buy them.  I use the heirloom varieties red and green deer tongue along with barcarole romaine and some red cos romaine.  I get my seeds from Seeds of Change.  Their seeds are grown out in a micro climate in southern New Mexico, which consists of all climates possible in the U.S., so their seeds grow well  no matter where I am.  Third, you'll need a nice shady garden spot under a leafy tree, preferably a fruit tree, but not a walnut.  Fourth, sprout your lettuce in the hot, sunny spot and let it get an inch or two and then transplant it under the shade.  Fifth, pick your lettuce when they're young, the heads about the size of your hands.  Keep replanting in soil blocks every week, about 4-8 blocks.  You'll have fresh salad all summer long with this method.  Remember soil blocks eliminate transplant shock, so summer's got nothin' on a lettuce transplant who will welcome the cool of some shade.