Remember that CA heat is bone dry. Sometimes the issue is not the heat, but the dryness. Check to see where they are native to; that often is very helpful.

With very few exceptions**, heat is not an issue for growing annuals.......in fact, most thrive on it. It is more a matter of sunlight and adequate water. Very few are going to be very drought tolerant regardless of how hot it might get :-)

**There are such things as cool season annuals (often half hardy perennials) that actually germinate and grow best in cooler weather. Snapdragons, pansies, calendula, nigella, annual lobelia are examples of some of these. They tend to die off in midsummer or in extreme heat but thrive in spring and fall. And in some cases, even into winter.

Also remember that annuals, which have to set seed, are very dependent on photoperiod. So again, it's not necessarily heat, but day length that dictates their behavior.

I have a book called: Heat-zone Gardening by the American Horticultural Society

it says for this plant:

USDA hardiness: zones 3-9

AHS Heat: zones 9-1

Soil: well-drained loam

Light: full sun

And, as others have said, water is the key here.