Yes, you should have been due duty of care, even for a WX-related delay. You can read more in the
EC261 / EC 261/2004 complaints, compensation and AA (master thread) thread.
Cheers,
LBBZman
UPDATED TO ADD: Actually, I'm not so sure of my statement. I went to read the referenced thread, and it's not so clear to me. YMMV.