I work outdoors and have fair skin so even in mid-summer I'm wearing long sleeve. These are very lightweight and breathable. I've tried all the "cooling" or moisture wicking and these are by far the best in comparison. They make a great undershirt as well during the winter.
I wear this underneath a short sleeve shirt, works great and the sleeves are tight enough to pull up and they won't fall back down, will purchase more in the future. At 35 bucks it is a little pricey though.
I purchased a few shirts to go bike riding in Moab,UT in Aug. Wanted something to cover the entire arm without having to worry about my arms getting fried. They worked awesome, never even broke a sweat. Wind blows right through them.
I bought this shirt to wear in late spring early fall when it has large temperature swings from cold to warm. This shirt does great job of wicking away sweat from the body. The one downfall to the shirt for me personally is that the sleeve cuffs are loose and aren't tapered or anything like the other carhartt shirts.