Our highest temperatures in the summer sometimes exceed 100F (38C). Are you concerned that 90F is too hot for Phrags?
I keep most of my Phrag collection indoors year round where the temps rarely exceed 80F (27F), but there are some that I have succeeded with growing outdoors in the warmer months of the year.
My P. longifolium, P. pearcei, and my P. Grande/Super Grande/"whatever they're calling this hybrid these days" all handle our temperatures well. I would suggest keeping the P. longifolium and pearcei wet, growing with water in the saucer and perhaps hosed down at least once a day. The Grande-esque hybrids can be fussy about water and temperatures, so you might have to approach with caution or be willing to try different cultivars or seedlings from different sources until you find one that's happy with higher temps. Also, it's best to avoid repotting Phrags in this kind of heat. Either try to repot them in the spring, or as early as possible in the fall once temperatures are more moderate but not yet cold.
In the past I grew most of my collection outside year round and for the most part the Phrags did alright. Perhaps I was lucky, though. For sure the flowers of besseae (and relatives) hybrids tended to produce pale or washed out colors and there's an overall higher incidence of being stunted or having developmental issues. In my experience, they do better indoors overall, though.