In general, loose-leaf lettuces are more heat-resistant and slower to bolt than lettuce varieties that form heads. I encourage you to try a butterhead lettuce first, followed by any type of green leaf, red leaf, or batavia lettuce.
Lettuce seeds become dormant when soil temperatures rise above 80°F (a condition called thermo-inhibition), which means they won’t germinate when it’s hot outside.
Whether you buy transplants or start them from seed indoors, make sure the seedlings are hardened off properly before planting them outside.
This will ensure a steady harvest all season long—as one group of plants starts to fade, another group can take its place.
Lettuce has shallow roots, so compared to other summer crops (like deep-rooted tomatoes), it needs more frequent watering (but in shorter bursts) when the days are long and hot.