I know, it's very confusing as I found conflicting websites as well. Some shows Windsor 6b whereas some shows Windsor 7a, St Catharines 7a, some even shows Pelee Island 7b ... Wow !
This website shows Windsor, St Catharines, Niagara Falls 7a, Pelee Island 7b
http://www.veseys.com/ca/en/learn/re...7mhnaoe012q070
This website shows St Catharines 7a, Windsor & Niagara Falls 6b
http://www.plantmaps.com/interactive...diness-map.php
But in both websites, St Catharines (Niagara-On-The-Lake) is in 7a.