Seas and swells won't hinder dropping anchor. *Currents* might make it tough to anchor in the right place, though.
But, yeah, if it was nasty at anchoring-time, it might even have been a case of "nevermind the forecast, it might get nasty again anyway".
BTW, the anchor isn't what holds the ship in place nowadays, it's the weight of the anchor chain lying on the bottom. The anchor is to help keep the chain untangled.