Freezing air temperature

Freezing^[1] or frost occurs when the air temperature falls below the freezing point of water (0 °C, 32 °F, 273 K). This is usually measured at the height of 1.2 metres above the ground surface.

There exist some scales defining several degrees of frost severity (from "slight" to "very severe") but they depend on location thus the usual temperatures occurring in winter. The primary symptom of frost weather is that water freezes. If the temperature is low for sufficiently long time, freezing will occur with some delay in lakes, rivers, and the sea. It can occur even in water supply networks, although this is highly undesirable and efforts are made to prevent this from happening.