I have 2 recommendations. The first is Cleome spinosa. Last year here in WTN, we had a 2-week period of 100+ temps, and it didn't rain for about 6 weeks (or longer). My cleomes continued to thrive with no watering and some grew to over 6'. Here, they bloom from early June until a moderate frost (sometimes withstanding a light frost), and the flower heads become more numerous as the plant matures. I love the exotic looking blooms, and the hummers love 'em. In the thread 'Cleome?' a few spaces below, bdriver also gives some points.

Cardinal flower (Lobelia cardinalis) is my other one. I grow them in 'bog planters' on my deck. I leave about 1-2 inches of space on top for standing water. I've seen them growing in some pretty funky water in my creek bottom, so you may be able to use grey water on them. The first photo below shows the rosette which stays green all winter, even in ice. The yellow stripe on the little female's head in the two other pics is cardinal flower pollen. She guarded the planters all Summer.

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I live about 45 minutes north of Atlanta. Last year I planted asters, French lavender & snapdragons. The asters died, but the lavender is still going strong, and the snapdragons have bounced back and seem to be budding. For variety, I'm going to plant violet lace lavender this year. I can't say that hummers would enjoy the lavender, but the butterflies sure do!

Russian sage (pervoskia?) does very well in drought, as does lavender - they're not the traditional red but my hummers like them. I'm not familar with violet lace, mustead does well here.

Remember too, that many plants that might normally be full sun might be better able to cope with drought if they have afternoon shade. Honeysuckles do well with afternoon shade. A newly planted honeysuckle will need more water than an established plant.

Butterfly weed - asclepias - and other milkweeds have long taproots, sedumscan tolerent some drought.

Geraniums are pretty tough - plant them in a LARGE pot in afternoon shade and they'll delight your hummers. The larger the pot the less often you have to water.

Don't forget a birdbath - if it's shallow enough hummers may investigate it and othre birds will definitely need it - I hope you get rain soon.