[Answered] – “so nice weather” or “such nice weather”?

Since “weather” isn’t countable, you can’t use “a” with it. So these are possible. Look at the word order carefully: The day was so nice that we took a walk at lunch. It was such a nice day that we took a walk at lunch. But NOT “It was such nice a day,” and not “It was a such nice day.” It was so nice a day that we took a walk at lunch.

 https://www.usingenglish.com/forum/threads/so-nice-weather-or-such-nice-weather.170352/