When we use the word 'such', is there a rule to dictate whether we need to add article a/an behind? For example:
I did not expect such cold weather.
I did not expect such a cold weather.
Another example I found is
She has such a marvellous voice!
All three examples are in the such + adj + noun form, only difference is the article 'a'. I would like to find out if there are any rules or is merely a usage issue?