For the spring/summer months, I made these two shawls with regular worsted weight yarn and used a large hook, US size N15-10mm. The larger hook really changes the weight of the shawl and makes it almost weightless, it's kind of amazing to me!
On a side note, I really need to get a lighter or a more comfortable grip for this size hook because the weight of this bamboo handle aluminum hook is pretty hefty and really wears out my hand quickly. I'd make more shawls with the same combination if I could get a better, more comfortable hook.
Both shawls are available for purchase on my Etsy site.