Being that this only happens when its cold; I would check that the fluid in there is of the proper viscosity. To thick an oil will become even thicker when it's cold. The pump will have a hard time pressurizing and circulating it. If unsure I'd change it out to the recommended fluid. The system is self bleeding and as long as you do not let the reservoir run empty during the filling and running of the system you'll be fine.
Even if they don't make it to Lake Ontario, they are as far upstream as Montreal. I may have to plan a trip to Montreal; you know, for the stripers... 😉