dietarily I get the most relief just eating milky/sugary things.. ice cream, yogurt etc.. Nothing hard in there todigest if you aren't lactose intolernat.
actually ALL DAIRY is a trigger for those with IBS, whether you're lactose intollerant or not. dairy should be 100% avoided by those on this diet. there are quite a lot of things in dairy that are hard to digest for IBS guts (check out the page on 'triggers' for more info on that if you're not sure why )
on the other hand, I find that small amounts of sugar (real sugar, not artificial sweeteners, which are triggers!) can help calm my stomach down a bit during/after an attack.
but stay away from dairy!
and to the original poster (Naturapanic) - stress + humidity would be my bet. those things alone always wreak havoc on my IBS, together they're even worse. just eat super safely and try to do as much stress relieving/relaxing things as you can, like meditation, yoga, quiet relaxation and other things you enjoy. also drink LOTS of water and try to stay cool!