Not necessarily.
It legitimately could have been weather if the plane he was scheduled to use was behind because it was in a city that had weather. (ex: his plane was coming from ATL and it was delayed because it couldn't initially get into Atlanta because of weather and naturally late getting out of Atlanta because of it.)
When I was flying I always told passengers the truth. That is what the company wanted us to do. I believe that is still what they want employees to do.
You may not see the weather where you are,
heck you may even be in the city with the "weather" (I'm looking at you NYC) and because ATC shut it down over a tiny cell that isn't over the airport the airlines are told the airspace is shut down due to weather.