much you can do to change the temperature, but you CAN help your plants survive, although tender, non-native plants are likely to wither away.
Resist the temptation to plant new plants right now, unless you’re prepared to give them extensive daily maintenance. Many plants are nearly dormant in this heat anyway. (As a Landscape Architect, I tell my customers who want to plant now just to dump them right into the trash, after buying them. They’ll probably end up in the trash anyway, and you’ll be saving a step.)