"Weird" means "strange". "Strange" has a widermeaning than "weird". You can call things that are not normal "strange" or "weird". But you can also use "strange" for something that you don't know about, even if it's normal:
There was a strange man on my back porch, so I called the cops.
This means that you didn't know the man. Even if he looked like a normal person, he would still be "a strange man" because you didn't know him and he wasn't supposed to be there. Another example:
If you see a strange package, inform the building staff or the police immediately.