It's warm in the summer, but it works both ways!
Shepherds in the desert have known the secret for centuries - wool is cool and breatheable in the summer.
As a bonus, wool reduces odor. Your tent partner will definitely thank you if you take light wool garments with you on your camping or backpacking trip.
Wool also wicks moisture away naturally, and dries much more quickly than other types of fabric. If you're light on packing space, you can wash it in the sink or tub and it'll be dry by morning.