Unfortunately, I'm busy for a big part of august, so if its not on the 1st it would be late august and then people are going back to school at that time. :S
So far it says Sunny for Saturday http://www.meteomedia.com/weather/caqc0363
With only 20% chance of rain, I might still bring an Umbrella, hope you come it'll be fun and don't worry you shouldn't get lost, if you know how to get to Mont-Royal, you just go up the slope and we'll be there ^_^