Yep. In August last year, during those sweltering first two weeks, I wore a long-sleeved wool tee shirt / base layer on a hike to Cascade Pass and back, which is about 8 miles and 2,000 vertical feet of ascent.

Wool pulls sweat away from your skin like a greedy sponge. Even in the summer, it feels wonderful. But this is another reason why you want thin base layers. Around 100 g/mm^2 is perfect; it adds almost no insulation, so it doesn't make you warm, just makes you not feel clammy. ( Plus, merino isn't all that warm. I've read that sheep wool is 1/8 as warm, per weight, as goat wool? )