Are they in pots? If so, remove them to a shady spot, you can water more but at some point the plants will slam shut their stomata and transpitation will slow way down, thats whats happening when a plant wilts due to excessive heat. The reason for the wilting is two fold, it reduces surface area facing the sun and is caused by decreased hydrostatic pressure as water flow is effectively reduced.
My greenhouse is hitting 105 American at peak daylight temperature for the next week or so. The way I combat this is greater soil mass. I water deep and less often. The idea is to sequester water deeper where the soil temps stay cooler and thus the root system is driven down a couple feet. I can water once every 3 or 4 days at 105 American.