My wife, who is from St. Vincent and the Grenadines in the Caribbean, says winter is "cold like a dog's nose hole."

 

 The Spanish version of “it’s raining cats and dogs” translates to “it’s raining pitchers”. Está lloviendo a cántaros.

Whenever I say it to Spanish speakers, they’re amazed that I know such a deeply cultural reference and ask me where and how I learned about it.
~

When I lived in a rural area, the locals said a heavy downpour was 'like a cow peeing on a flat rock'.

Colder than a witch's t*t.

Crystalline dihydrogen monoxide is gravitating toward the surface of the earth at a most heinous rate.

Brass monkey weather (raw cold). From "Cold enough to freeze the b+++s off a brass monkey". I have no idea of its origin; and can't imagine why a cold day might castrate a brazen simian.

Perishing -  for describing brass -monkey weather in  polite company.

Baby weather (wet and windy.)

Lazy wind - the sort of cold Winter breeze that feels as if it's cutting through rather than going round, you.

Bracing - a euphemism for a cold, sharp breeze or chilly sea-water; often associated with the gritted-teeth "we're-here-so-enjoy-it" English seaside resorts on the chilly North Sea rather than the balmier Southern and West coasts.

British regional dialects include the Northern English siling down, for when it's raining cats and dogs; and pea-souper, (London, I think) for dense fog, or maybe more especially the smog now virtually unknown there.