No advice on clothes, etc, but I sympathize with the heat/humidity and its effects on asthma. We visit relatives in Georgia a couple of times a year, and it's brutal on my lungs in the summer.
So, my recommendation would be talking to your pulmonologist ahead of the trip and maybe revisiting your prescriptions. If you aren't taking a daily maintenance med, consider it. I've used Advair in the past (pricey) and am now on Breo (amazing and cheap!). When I take these inhalers daily I have little need for my rescue inhaler, even in hot & humid weather.
Tara
living a crazy life with 3 boys
I am thinking now
of grief, and of getting past it;
I feel my boots
trying to leave the ground,
I feel my heart
pumping hard. I want
to think again of dangerous and noble things.
I want to be light and frolicsome.
I want to be improbable beautiful and afraid of nothing,
as though I had wings.
~Mary Oliver