Water droplets continue to exist in liquid form, unless they have something to freeze onto, until the temperature drops well below -10°C when the droplets will freeze to become ice crystals.
Ice fog is a phenomenon common only in the arctic or Antarctic latitudes.
Ice Fog is usually found in shallow layers. A pilot may be able to see the surface through the fog from above and believe that he can land without difficulty. However, as the aircraft descends into the fog at the flare, the pilot can find himself unable to see more than a few metres. The pilot should therefore take note of the reported visibility on the ground and reports from aircraft ahead of him.
Ice fog can be formed by hot, moist, exhaust gasses from vehicles and aircraft. It is not uncommon, on a clear cold day in the Arctic, for an aircraft to generate so much ice fog on take-off that subsequent aircraft have insufficient visibility to take off themselves.