On a temporary basis - no problem. I would not recommend outdoors as a permanent site, however - especially here. Right now on my patio is is 100 degrees F in the shade. But, there is no moisture problem unless it falls in the pool or a T-Storm drops in.
I frequently run my laptop on the patio in the evening when it cools down a bit. It's very nice, and my aircard gets a good EVDO connection.