[Scott from the Left Coast]

Well, that could've been some of it. It's overcast and wet and cold (it doesn't get muggy here much, here when the air's saturated, usually the temperature is cool to cold). But cold overcast in May isn't the most uplifting weather, so that might've had an effect (it was wet and cold, but even worse, yesterday).

[Fedora]

That sounds like what we have except it's a bit warmer; very damp, though--"muggy" might not be the precise word I'm looking for but it's very damp in a foggy, London-like kind of way. It's not helping my sinuses, either!