Years ago I met a new GF because she was told to get plenty of sunshine to help with her psoriasis. Sure enough the AZ sun helped her. When she moved back to the Northeast, then she started using sun lamps.

Yes this was way back, 30 years ago, and we know much more about sun lamps now.

This may not be an option for you with heat. However, I wonder if full spectrum lights would help you? You know the kind they sell for people with seasonal light disorders?

It was really tough for my friend. She had psoriasis that related to her arthritis. She was dx at 16 with this. When her arthritis kicked up, so did her psoriasis. One reflected the state of the other. Talk about life being unfair!!!