The Tempest is not too much tent for a winter on Mount Hood, where the weather can be fierce. But it’s certainly too much for the summer. I imagine your volunteer duties cover something like June to September, right? And you’re not traipsing around the mountain, are you? Instead, you’ll be staying around or below the tree line. For that, you certainly won’t need a Tempest (a fine tent, but at $500 a little pricey).
Instead, I’d consider a lesser, bigger tent. Lesser because you’ll pay less, and the fact is that four months at elevation will do considerable harm to any tent due to ultraviolet rays from the sun. And bigger because, as you say, it’ll be home and I assume you’ll be working from a base camp of some sort. So look at something like Sierra Designs’ Alpha CD ($349), a three-person (for more room) “convertible” tent that can bridge climate shifts nicely. And it’s less than eight pounds, so not too onerous for one person to lug around. Or, look at Mountain Hardwear’s Hammerhead 3 ($315), which is a true three-season tent but well up to the task of an extended stay on Hood. If you really want a four-season tent, though, and the price is not a real object, I think the Tempest would serve you well.