If you're not doing anything on Saturday afternoon, a water gun fight is being planned for outside city hall.
About 100 people have confirmed their presence on Facebook (which usually means about 10 people will show up).
It's at the fountain at Place Vauquelin, which is just outside city hall on Notre Dame St. at Place Jacques Cartier (Champs de Mars metro), at 2pm.
Weather so far calls for sunny sky and 25 degrees.
UPDATE: Turnout was better than I expected, a good 50 or so. My pictures are below in a slideshow or on Flickr.
There are also photos on Facebook.