In my experience of claiming against EZY, they have a standard policy of denying all claims, (unless they have been caught "bang to rights"), at least twice. They initially denied my claim, even though it was caused by them wrongly scheduling crew!!!
So that was letter one.
Your reply should both ask for proof of what they said, and point out that weather has been found NOT to be extraordinary. Weather and its variations is normally quite ordinary.
They will deny it again.
So you write your third letter to the CEO at their Head Office.
They do try to respond to CEO letters.