How does hardwood floor acclimate to a location with variable humidity?
Humidity is variable everywhere. I live in the desert where the indoor humidity varies from 10% to 60% depending on the time of year. I've installed engineered hardwood and it's totally fine. Don't most houses in the northeast have hardwood flooring? I think you'll be totally fine too. Just keep in mind seasonal cycles; if you install during a high-humidity period, expect it to shrink a bit. If you install in a low-humidity period, expect is to expand a bit.

That said, hardwood flooring isn't a the best choice for a building that's not temperature controlled at all, as you've implied.