I ordered one of these shirts to try out on a three day hiking trip. It was great! Even though it was in the 90s, I was fine wearing this shirt - better than fine since I wasn't constantly worrying about sunburn (I am very fair skinned). I am planning some more hiking trips this summer and am about to order 2 more of these shirts. In case it helps anyone, I am 57 and 125 lbs - I ordered both a small and a medium to try out the sizes and small worked best; I could wear another tank top and my sports bra under it with no problems. I was swimming in the medium size and will return it.