Welcome to the forum I'd consider 3 things to make a suit wearable in tropical weather.

Weave - Fresco is a more porous weave and is a good choice for summer suits. You may also pick something with mohair in it but this adds to the coarseness of the fabric.

Weight - Anything around 300g is fine I suppose but I'd avoid the super lightweights (250g and below) as the drape will suffer. Take a look at the Uniqlo linen jackets and you'll understand.

Lining - Naturally you'd want to go for half lined or even unlined suit. Also the lining material makes a difference. I'd take Bemberg anytime over silk or polyester (!).

Just my 2 cents, perhaps you'll find better answers in the other menswear forum (look for kotmj's signature).

This post has been edited by deriku: Jan 5 2013, 03:30 PM