Yes, people with auto-immune diseases often find their aches and pains increase with sun (or fluorescent light) exposure. I also find my temperature has a tendency to shoot up if I'm in the sun.
There are several lines of sun protective clothing (Coolbar comes to mind.) Also, of course, there are hats! And sunscreen. And a couple of brands of sun protection that you add to your washing machine that then produces sun protective clothing.
Stay in the shade - also remember that any body of water is a huge reflecting pool and you'll get more sun around water. Keep your body cool - lots of ice water!
That's all I can think of right now - will add more if I think of it. You can also use the search feature to search for "sun" to see older discussions on this topic.
Lynnwood, Lupus & Sjogren's Moderator, Dx: 2000DIAGNOSING LUPUS & HW's LUPUS 101
"Life is far too important to be taken seriously." - Oscar Wilde