Patagonia First Sun Jacket

The hood covers head, back, and sides of neck for great sun protection, cooler than a hat. I use as a shirt, a bit heavier than some hiking shirts, but the hood is great.

Sells as a jacket, so probably want a size smaller, and still get a relaxed fit for venting.

Hands can be pulled inside cuffs for sun protection, if not holding something. Hood can be pulled down for more protection or not. Front unzips for venting, though that exposes skin to the sun. Elastic cuffs can be slid up arm to ventilation as well.

Not waterproof, but dries quickly with just body heat.

Nice zippered side pockets can hold more than what you would want to put in them.

You could layer with this, it if cool but sunny for instance. Not sure why you would want to do this otherwise, though it could add a bit of warmth in a layering system.