Let me start with I don't know your climate or how hot it gets there in the summer (AHS zone would be a better indicator of your summer temps).

However, if you can grow lettuce at all in the summer, check for bolt resistant varieties and try to give them shade during the hottest part of the day. Taller plants can help with that sometimes.

Experiment and good luck!

I know buttercrunch variety is heat resistant. There are some. I went through my packets and searched the names of my lettuce and read if they were heat resistant or not. I am in zone 7 (getting to the highs of high 80s to low 90s now) and even the buttercruch went limp in the shaded heat so I took it inside (we keep our house in the mid 80s).

I will get my list from home and share what I have learned on which types of lettuce is heat resistant.

Learn something new every day! I had not heard of the AHS heat zone map, but that makes perfectly good sense. I am in AHS zone 5, with 30-45 days above 86 degrees. We have had several low 90's days so far this year, and all my greens bolted in the past week. I had planted a letttuce mix of black seeded simpson, green salad bowl, marvel of four seasons, and bibb - plus some arugula. So far only the bibb hasn't bolted.

It looks like buttercruch and bibb are closely related, maybe? They are listed in the Johnny's seed catalog together, and several varieties are listed as heat tolerant. They also list varieties under the category "summer crisp". I guess I should order a package, plant them out, and see what happens.

Good luck. I am in AHS zone 2, so shaded lettuce that's well watered does ok here. Glad you found what you're looking for and learned something new. Take care.

Deer tongue lettuce was another type that said it was heat tolerable.

I didnt know about the AHS zone either. I am in zone 7 as well as the hardiness zone 7 (I think that is right. Maybe I have my zones mixed up).

I planted some new spinach in shade and they are curling up now. I wonder if it is too hot outside for even those in the shade. I hope not. That kills all my salad veggies.

Johnny's sent out a mailing today listing some of their heat tolerant lettuce varieties. I think that here in central Texas it is too hot for any of them (I have planted even more heat tolerant greens instead, such as molokhia, vegetable amaranth, and purslane), but perhaps you may have more luck with these recommended summer lettuces.

"Lettuce prefers cool temperatures, but by sowing every week, choosing heat-tolerant varieties, and using shade protection, you can produce lettuce right through the heat of summer. Careful variety selection is important for hot weather crops."

Adriana Lettuce (Green Butterhead)
Ermosa Lettuce (Green Butterhead)
Nevada Lettuce (Summer Crisp)
Cherokee Lettuce (Summer Crisp)
Green Star Lettuce (Greenleaf)
Tropicana Lettuce (Greenleaf)
New Red Fire Lettuce (Redleaf)
Vulcan Lettuce (Redleaf)
Coastal Star Lettuce (Green Romaine)
Jericho Lettuce (Green Romaine)
Concept Lettuce (Green Summer Crisp)
Magenta Lettuce (Red Summer Crisp)

Here is a link that might be useful: Johnny's selected seeds - lettuce

New Zealand, Marabar. They love the heat

Here in Alabama, I have 7 different kinds of lettuce growing (bibb, romaine, salad bowl, iceberg, etc. - and get tired of eating salads by the time that summer arrives. Lol