I have PsA with some possible evidence of RA, as well. I currently live in Santa Cruz, CA, where the weather fluctuates a lot, both throughout the year and during the day (everyone wears layers; it can go hot to cold, sunny to cloudy and windy, in the same day). I've had symptoms of PsA for ~6yrs, but only was diagnosed a little over a year ago. I'm currently on Methotrexate and Enbrel, with little results. My condition has deteriorated quite rapidly over the past year. I hurt in just about every joint, as well as the tendons and ligaments in my hands and arms. I'm no longer able to work; it's hard to find a comfortable position for more than a few minutes, and it's hard to do basic functions (like writing, using utensils, getting dressed, brushing teeth, etc.).
My husband and I went to Fiji last October for our honeymoon, and the heat made it possible for me to actually go for walks (I was on Sulfasalazine and Methotrexate at that point), but it was so humid I didn't really want to leave the air conditioning. My doctor thought that the humidity probably helped more than just the heat, but my husband and I recently went to Death Valley, and I felt great! I was able to wander around the desert, taking pictures, even hiked a little, so dry heat helps, too (thank goodness, because humidity sucks).
So now we're thinking that we should move to a hotter climate. Since we haven't stayed somewhere hot for more than a few days at a time, I thought I'd check if other people have found that a hotter climate helps, or if my experiences were just coincidence. Also, does the the humidity help more? I don't really want to live in a humid area, but if it helps, I'd do it.