coldest
adj.adj. the lowest possible temperature compared to everything else. You use this to describe the most freezing day or place.
adj. the superlative form of 'cold'; representing the lowest temperature in a specific group or range. Functions as the extreme point on a scale of thermal intensity.
January is usually the coldest month of the year.
The researchers recorded the coldest temperature ever measured on the planet at a remote station in Antarctica.
Even in the coldest reaches of the deep ocean, specialized organisms have evolved to thrive in temperatures that would prove fatal to most terrestrial life forms.
Superlative form; typically preceded by the definite article 'the'.
the most coldest daythe coldest dayShort adjectives like 'cold' form the superlative by adding '-est' — do not use 'most' with the '-est' ending.