Question

What a lovely weather!. change in ​

Answer 1

Explanation:

What a lovely weather" is not good English in either the US or the UK. " Weather" is a non-count noun. You can't have one weather or two weathers or three. So you can't have "a" weather. Only the version without the "a" is correct: "What lovely weather."

Answer 2

pura question likho than l will answer you ok