Weather upstream from your flight can still be responsible. If the aircraft your flight is going to use gets delayed due to weather earlier in the day, that's a weather delay, even if you had clear skies at your departure.
Airlines aren't responsible for weather delays, full stop.
Not even. If air crew is unavailable because a previous flight ran long due to headwinds and they are out of allowable flying hours for the day, week, or month? That's "weather-related" and you get nothing.
I agree, I could have been clearer by repeating the exclusion for weather delays on one or more line items. I'm sure there are even borderline cases where a denial by the airline might be questionable and your only course of action would be to repeatedly and/or strongly state your case, escalate the matter up the chain-of-command, call/file your case with the government (e.g., DOT ACPD), file a request for arbitration (i.e., if your ticket requires), file a small claims suit, etc.
Airlines aren't responsible for weather delays, full stop.