Any chance that you could have a mislabeled plant and this one is supposed to naturally bloom late? Do you know the name of this azalea variety from the plant's label? Can you post pictures of the shrub and close-ups of the blooms? Some native azaleas flowers late and can have yellowish hybrids.

Some yellow deciduous azaleas bloom very late.
One such variety is Weston's Lemon Drop.

It wasn't labeled when I bought it one spring when it blooming. It continued to bloom in spring the next couple of years. But it is a taller variety, deciduous and does resemble Weston's Lemon Drop.

Varieties of R.viscosum, one of the parents of Lemon Drop, bloom late; anywhere from mid-May to early August. See Lemon Drop below.

Here is a link that might be useful: Lemon Drop, courtesy of Weston Nurseries