On the maps on the website, the blue dot will represent the location that you visited most recently. For example, if you are viewing the forecast for Winnipeg and then you click on the map, the blue dot on the map will be on Winnipeg.
If you navigate to the map without first visiting a location, the blue dot will represent either the location you visited when you were last on the website, or the detected location of your device, which uses the IP address. Sometimes this can be different from your actual location, depending on your internet service provider.