I picked Zinnias last year from June to October, maybe longer. Incredible. They got to be almost 6 ft tall, despite constant cutting of bouquets.

Alstromeria blooms nearly all year, if it doesn't get hit by hard frost and if the temps don't go over 95 for too long a period.

ditto on zinnias.

Delphinium, but it wouldn't work in your heat! Rudbeckia are also good that way, especially the so-called annual varieties, which are biennial or short-lived perennials here. And they LIKE heat.
Jeanne

Gaillardia, it's blooming now and doesn't stop until November.

GGG