So and that???

It was that cold would refer to a certain degree of coldness, as in I could feel icicles forming from my nose. It was that cold. (That's how cold it was.)

It was so cold means It was very cold.

Thank you Gus I got it...one more question ...I am being expert and i am becoming expert. Are these sentences have same meaning??
thanks in advance

I am being an expert.
I am becoming an expert.

Only the second is normally possible.

Also, note that 'it was so cold' as a complete statement meaning 'very cold' is not acceptable in careful writing, because 'so' requires a 'that'-clause of equivalence: 'It was so cold that my beer froze.'

I have never drunk so much wine in my life. This sentence make me confused as why 'so' is used there? or it doesn't mean 'very' here?

Thanks in advance

vts nairI have never drunk so much wine in my life. This sentence make me confused as why 'so' is used there?

It is informal.

vts nairit doesn't mean 'very' here?

It means 'I have never drunk so much wine [before] in my life [as I have in this case].'

'So...as' is a common negative variant of 'as...as'.

I have never drunk that much wine in my life. Does this make any difference from above sentence? pls explain

vts nairI have never drunk that much wine in my life. Does this make any difference from above sentence?

No, no difference.