Lululemon is the best for this. You can tell that "where does the phone go" is an important step in the design process for most of their products. Most of their guys clothes have an extra little spandex sleeve inside one of the pockets to snugly hold a phone and keep it separate from whatever else you put in that pocket.

Running belt. Better than the fanny pack suggestion, more concealable if your shirt is untucked.

I, personally, just choose the fashionably unpopular option of cargo shorts. But if I had to come up with something else, I'd use my running belt.

A vest with zipper pockets is my go-to all weather solution now (outside the hottest of climes)

I can CCW a full size 1911 in summer clothing, so an iPhone should be simple.

The nature of iPhone access is very different: you want to make sure you feel the phone go off, and it's culturally acceptable, so concealment isn't a concern, which means that 'summer clothing' can include fitted shirts and needn't include a belt.

Making concessions in your attire for the sake of your hobby is a necessary evil. That isn't the case for phones.

neon fanny pack.

Lip plate: https://en.wikipedia.org/wiki/Lip_plate