Hi Bill – temperature and humidity certainly do matter when applying any coating. It will effect the way the coating flashes during application and how it cures after application. 10C is about the coldest I would say you should consider applying the coating, anything lower is too cold. I would recommend above 16C if possible. I also would not warm up the panel with a heater as this could lead to inconsistencies that will be hard to adapt to while you’re applying the coating. If you can heat the entire room you will be working in to a more suitable temperature and leave the car inside long enough to warm up to that temp, then that is preferred.