The smell was reported across Leeds city centre, near Elland Road and as far as Cottingley Crematorium in LS11.
One resident on Facebook said: "Around midday today there was a strong smell of cannabis in Leeds 15, to the point all our windows had to be shut.
"It would seem my kids at school smelt it and my husband at work at the other side of Leeds city centre smelt it too all around the same time, very weird.
"Did anyone else smell it or have any idea where it was from?"
Hundreds of Leeds residents replied saying they could smell the strong scent across the city.
Leeds resident Joel Clark tweeted: "Why does all of Leeds smell of weed? It stinks!"
Another user commented: "I was driving towards White Rose earlier and could smell weed really strong".
It is not yet known what caused the smell across the city.