Watched a whole batch of coasters crack like ice last winter. My shed dipped below 50, and the polyurethane just gave up. It looked like a spiderweb on every piece. Now I check the forecast before I even open a can. Cost me a weekend and a lot of sandpaper.
Temperature is only half the problem. Humidity swings during curing will do that too. I keep a cheap thermometer and humidity gauge right on the workbench now. If the numbers aren't right, I just wait. Sanding that mess back is way worse than being patient.