The first 3-4 days I kept this young petunia plant in the shadow, placing it on a north-west side exposure, after a few days. The later was a big mistake.
In the extreme heat of these last weeks, half of the flowers wilted until next morning, though it was getting only an hour or two of late afternoon sun.
Petunias should bloom throughout the summer, so I'm deadheading it diligently hoping that it will restart branching and opening its new buds.
If the weatherman is righ, some rain will cool down the temperature very soon.