I seriously doubt it is from high temperatures.
Welcome to NGA
@MrWisteria.
Two things right off. Have you fertilized it this season or added compost to the soil?
Have you checked the leaves for scale or aphids? Those are both causes of leaf curl.
How often do you water? If you find aphids you can wash them off with a strong spray from the hose.
It is always best to identify a pest and then use the proper means to rid them from your plant/garden.
Hope this is of use. Regards
