Cold
Cold is one of the Problems in Frostpunk 2. Cold grows if people cannot find access to 
Shelter and 
Heat, leaving them worse for wear if they are not protected from the frost.
Lacking Shelter can be one of the main reasons for this Problem increasing rapidly. Make sure that enough 
Housing Districts are built and then for complete protection, make sure that the Districts' Demands for Heat are fulfilled to prevent the issue. Another likely cause of increasing Cold can be Temperature drops and Whiteouts, especially if not enough fuel is stockpiled in the City to meet the surging demand for Heat.
High Cold increases 
Tension, increases the 
Disease problem, decreases Population Growth and can cause recurring events of citizens Freezing to death. Unlike some of the other problems, there is no building that addresses cold directly; it must be solved by fixing the underlying issues with Shelter and Heat.