Viscosity is an important factor in quality control when it comes to painting. Different viscosities will yield different results, so if you want a consistent result in the finish of a painted surface, you must know the ideal viscosity of your paint, and then do everything technically feasible to maintain that viscosity.
Viscosity itself, however, is prone to many factors, and temperature is a key element. While specific numbers will vary, higher temperatures mean lower viscosities, while lower temperatures mean higher ones. And all of this comes into play at the most critical moment of all: right when it’s time to apply the paint to the surface.