Before I've read you message I was sure that dry air slows down transmission speed. But indeed, it's humidity https://papers.ssrn.com/sol3/papers.cfm?abstract_i

Before I've read you message I was sure that dry air slows down transmission speed. But indeed, it's humidity https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3551767 https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3551767