There are plenty of cancellations and delays in the winter not only because of an event at the airport you are at but also at other airports where there are delays that prevent inbound aircraft for your flight from arriving. If you are on Air Canada, then even if there is a delay of the inbound aircraft there are usually spares on the ground and substitutions can be made that provide an alternative. If it is an airline based elsewhere, then you have to wait for the scheduled flight to arrive, which may involve a longer delay. There are also outbound delays due to de-icing. You won't know until the day you travel what the real story will be. Weather forecasts are usually wrong.
Understood. Part of the reason ORD is so bad is because of issues like this. I am less concerned about the issues at other airports because my flights are direct from LAX and the outbound aircraft should be coming from Asia. It's the landing and leaving YYZ that had me most concerned, which seems is valid but perhaps a bit overblown. If I don't get a more optimal route I guess we will just have to plan for potentially having to stay in Toronto for a couple days. Maybe we will plan a weekend stopover in JFK or YYZ on the way back and make the most of our winter clothing.