Too hot this time of year. We just have to wait for cooler temps.

Growing lettuce in the summer is probably possible, but would require so much effort it wouldn't be worth it to me. I'm trying to find leafy greens to grow instead of lettuce in the summer. The Malabar spinach, Okinawan spinach, moringa, and other heat tolerant crops are not as tasty as well grown lettuce, but they do offer a nutritious addition to salads.

Haven't done it, but I understand 1 approach is to sow thickly & harvest small - i.e. 'baby lettuce'

From what I understand it can be done hydroponically, I have not tried it myself. In the summer I eat okinawa spinach, green gynura, the large leaf edible hibiscus, katuk, and water celery leaves. If you have a mixture of this type of greens they are delicious especially with some everglades tomatos.