In Baltimore,Maryland---
I had an old apartment that had pine wood floors,tung and groove. I used coarse,medium and fine sandpaper and did it going WITH the grain of the wood then used a rounded sander for trimming the edges. I used the straight,glossy,clear polyurethane and a wide horse hair brush to apply.I did not use the water base and don't recommend it. I put down four thick coats and let it dry with good ventilation. the drying took almost 12 hours but was beautiful and lasted the 7 years I stayed there.To clean my floor,I would vacuum up all the dust then use my commercial mop and boiling hot water with a wringer attachment on the bucket with MR Clean or dishwashing liquid but only a few drops.I thoroughly wrung the mop and as I mopped the floor,the steam from the mop dried the floor fast and made it shine. I did this twice a week and never had any issues with warping or losing the finish.It looked just as nice after I left as it did when I originally refinished it.I think the thickness of the poly along with the way it sealed the wood had a lot to do with the strength it had acquired