I live in the central valley about 160 miles south of Sacramento, with similar heat related problems in the summer. I've had success with Warsaw Nike as a lovely purple with a faint red hue (sort of royal purple, with a velvety texture). For me, it produces a mass of blooms in the upper several feet in May. Last year toward the end of May and this year the first week in May. It has contrasty yellow anthers. There is a lesser flush toward the end of August. I've combined it with Justa, which is a smaller medium blue, with yellow anthers. It blooms at about the same time in May as WN and lasts most of the summer. Justa is advertised at 4-6' but grows to about 7' for me. Both have been able to handle the heat, but both need a tremendous amount of water and WN needs a lot of food. Good luck...