I’m no sure we can help. Our hexayurts are not waterproof. The 4 x 8’ polyiso panels we use to put them together are NOT manufactured to be used outside. They are used inside the house - between outside covering and inside sheet rock.
Also, as we have learned during rainy moments at Burning Man they are not leak proof without a lot of extra tape that doesn’t necessarily like water.
They might last a month in this current weather. (I’m in 707) Not likely through the rest of our Northern Calif winter. A friend put one up a couple years ago in Sonoma and it did not make it through the winter.
I know it’s not what you wanted to hear, but it’s the truth from my experience & perspective.
I’m sorry, wish I could offer more. Peace, Hal Black Rock Hexayurts