Spring through early Summer are best, it gets warm but not really hot. The problem is the dust can be really thick in spots. One trip we wore masks, made it much more bearable.
Wes - reservations are really needed unless you are going on the major holidays. Even then we've been able to get them. The pic seen of the rigs is at a shady site, others are more open.
Right now they have water, but they are working on full hook up's sometime in 06 hopefully. They are also putting in cabins.
I have the alt need to reinstall my map software and I can get it. No rejetting is needed, its at the base of the blue mountains near Heppner, OR. There is a park down the hill that allows for dumping too, I think its only $2.
I'd love to hook up with folks, we'll probably be heading up there about once a month and more is always fine by me too.
Oh here is what the dust looks like when its really bad.
I have more pics if you want to see them just click
here.