For anyone confused, when Lento asked if it "was going to snow today" he wasn't actually trying to ask about the weather. He was asking a rhetorical question which, as the tl note stated, was equivalent in meaning to asking if pigs were going to start flying.
I realize that all of that is a bit confusing, so I'll give an example of a way the interaction between the two could be refrased:
Lento walks in and sees Lorraine cooking. Lento, in reaction to this, Lento jokes that he didn't know she could cook. Lorraine responds by saying that she can cook basic dishes.
She then reveals that she isn't cooking a basic dish. The humor of this interaction is furthered shortly after when Lento exclaims that the food is good and saying that he didn't think that food would taste so good.
This shows that Lento couldn't have expected the meal to be so scrumptious. This in turn means that his expectations were, at most, not set very high, despite the high quality of ingredients and when this is coupled with the later revelation that Lorraine had included blood, which Lento, a zombie (or whatever you call it) would naturally find to be of good taste, it implies to the reader that Lorraine is actually total shit at cooking and Lento doesn't notice because of the blood's effect. Ironically, as a result of this perceived good taste, Lento mentions how he feels more human, not knowing that this perceived good taste is a direct result and indicator of his newfound inhuman body.
Coincidentally, in Mary Shelley's Frankenstein...oh dear, it would seem like I've spent way to fucking long writing this, I'm afraid I can't continue any longer.