You can probably use some of the suggestions specifically developed by the wholesaler that developed Encore Azaleas for the North Central clayish and hot area. See the information on this link:

https://encoreazalea.com/plant-care/how-to-care-for-encore-azaleas-in-north-central-texas/

Basically, you build a raised bed and amend the soil to keep it either acidic or less alkaline. Azaleas tolerate some alkalinity so it is not a necessary to bring the soil down to very acidic levels of pH 5 to 6. You have to acidify the soil forever as long as you have the azalea there. I start with the garden sulfur product's instructions and, if it lowers the pH and then the pH level gets stuck, I know I need to start increasing the amount of the product if the leaves still show signs of iron chlorosis. Liquid products correct the problem faster but need to be reapplied more often. But proceed slowly with increases in the amount of product used beyond what the product label calls for because azalea roots are shallow and tiny so you do not want to burn them by dumping a lot of sulfur. You can also use iron-chelated liquids, greensand or iron sulfate but aluminum sulfate can be toxic to azaleas/rhododendrons if used in large enough quantities. I observe the azalea foliage for signs of iron chlorosis (the leaves turn light green or yellowish except for the leaf veins which remain dark green) and always amend the soil in Spring and sometimes in early Fall to keep them happy. See what works with your soil. You can use soil pH kits with numbered results to monitor the results and write them in your wall calendar so you keep abreast of how things are going and if the azalea soil needs amending. Maintain 2-4" of organic mulch under the azalea at all times but be careful stepping over their tiny and shallow roots when gardening nearby. They should develop flower buds for the next year sometime after blooming so if you ever need to prune it, do so after blooming ceases in Spring. Pruning in the Fall will just cut off the flower buds for next Spring. The leaves might turn a reddish brown Fall color or mahogany wood color in Spring. Although it is evergreen, it may shed foliage in winter in cold enough zones.

https://www.thespruce.com/stewartstonian-azalea-shrubs-2132705

Here is a highly detailed map of US soil acidity:

http://www.bonap.org/2008_Soil/pH20110321.png

Unfortunately this variety is prone to part of the petals looking as though bleached after the flowers have been open for a bit. This happened every year at my previous habitation. To plants located north of a landmark coast redwood tree, so that there was no direct sun exposure until late in the day. In a cool and dull maritime climate.

So I eventually removed the planting. If you are in an area that would be warm and bright during flowering I would definitely consider placement carefully. In relation to where the sun hits at that time of year.

Embo can you recommend a red azalea variety that doesn't do that? They all do to some degree in my experience. My neighbor has a big 'Stewartstonian' (I suspect) in his yard. The flowers on my 'Floreamore Red' seem to last longer before bleaching, but they still do so after about a week. https://www.houzz.com/discussions/6115565/continuation-of-some-garden-pics-mostly-of-ericaceae