 Don is using irony. He said that the weather is lovely, but he thereby meant that the weather is terrible. So he implicated that the weather is terrible. Implicating is an illocutionary speech act, something done in or by uttering words (Austin 1962: 98–103). Since it involves meaning one thing by saying something else, it is an indirect speech act, albeit not one that Searle (1975: 265–6)  analyzed.[2]