Sweater Weather.
Usually in Fall weather that is perfect for a sweater.

A term used to reference cannabis/marijuana/weed.

Fall weather that is just chilly enough for a sweater, but not cold enough for a coat. It is the perfect sweater weather. Most people enjoy sweather because of the juxtaposed chilliness of the face and hands with the warmth of the body under the sweater, much like people enjoy a warm blanket in a cold room. Very few geographical locations experience perfect sweather for long periods of time, so sweather is usually accompanied by a lot of talk about the beginning of sweather, upsales in sweaters, and a rise in talk of fall fashion.

"sweater weather" when it is cold enough that one begins to wear sweaters.

The proper way to spell "sweater."

Noun.
Regarding a specific sweater and the weather at the same time

Another word for obscene incompetence, or absolute fuck up. Originated from a mass produced/distributed mug which meant to read, “Sweater Weather,” and instead read “Sweater Sweather.” Can be used in noun, verb, or adjective form.