If you have insulated your excavated site, then you’re already ahead of the curve. It is not possible to effectively pour a safe foundation if the ground is frozen so if your insulation efforts failed or if you didn’t plan for insulation, you will have to thaw your site with heaters before proceeding. Before you get started, you should also ensure you are using a weather-appropriate concrete mix and that you are storing your dry mix and tools in a warm place before use. Once your foundation is poured, you’ll still need to keep the concrete from freezing for at least 24-48 hours. The concrete curing process is temperature-sensitive and failing to keep your new foundation from freezing will permanently damage the strength and durability.