User blog comment:Xilinoc/Ch. 567 (Rukia be like "I ain't even scared though")/@comment-10554972-20140205203959/@comment-26420452-20140206181144

Ah, I see where it comes from.

However, there's a misinterpretation. What Hitsugaya meant in chapter 358 is that he doesn't need the air to be moistured in order to use Hyōrinmaru, because he has power over weather and can bring clouds from elsewhere.

In chapter 507, Tōshirō notes that he couldn't use Hyōrinmaru anymore because the air of Seiretei started to dry up.