My fashion routine doesn’t change too much during the summer months, except with more tank tops and light colors. I say goodbye to black and other dark colors until the cooler months, which could be a long way away.
Cotton is key! No more poly-cotton blends for me, except in sleeveless. No more pure polyester, only rayon and cotton, and mostly cotton. Cotton is breathable and light. And, on a slightly grosser note, both absorb sweat and dry quickly, so there’s little to no discomfort from wet armpits.
The sleeves don’t go either. I use short sleeves during extremely sunny days or bring a short-sleeved piece to go over sleeveless, to protect my arms and shoulders from the blaring sunlight. Sunburn is no fun. Long sleeves can even still work too, provided it’s a very light and breathable material, usually rayon.